The year 155 B.C. was signalised by an important event, if not in the history of ideas, at least in the history of their diffusion. This was the despatch of an embassy from the Athenian people to the Roman Senate, consisting of three philosophers, the heads of their respective schools—Carneades the Academician, Critolaus the Peripatetic, and Diogenes the Stoic. Philosophic teaching, once proscribed at Athens, had, at the time of which we are speaking, become her chief distinction, and the most honourable profession pursued within her precincts. It was, then, as natural that an important mission should be confided to the most eminent representatives of the calling in question as that high ecclesiastics should be similarly employed by Rome in later ages, or that German university towns should send professors to represent their interests in the imperial Diet. But the same fate that befalls an established religion had befallen an established philosophy. An attempt to impose restrictions on the liberty of teaching had, indeed, been successfully resisted, and the experiment was never repeated.212 Nevertheless, the teachers themselves lost as much in true dignity as they gained in affluence and popular estimation. In all probability, the threat of death would not have induced Socrates to undertake the task which was, apparently, accepted without compulsion and as an honourable duty by his successors. The Athenians had made an unprovoked raid on the town of Oropus; the affair had been referred to arbitration; and the aggressors had been sentenced to pay a fine of 500 talents. It was to obtain a remission of this sentence that the three Scholarchs were sent on an embassy to the Roman Senate.
If the nature of their errand was not precisely calculated to win respect for the profession of the Athenian envoys, the subsequent proceedings of one among their number proved still less likely to raise it in the estimation of those whose favour they sought to win. Hellenic culture was, at that time, rapidly gaining ground among the Roman aristocracy; Carneades, who already enjoyed an immense reputation for eloquence and ingenuity among his own countrymen, used the opportunity offered by his temporary residence in the imperial city to deliver public lectures on morality; and such was the eagerness to listen that for a time the young nobles could think and talk of nothing else. The subject chosen was justice. The first lecture recapitulated whatever had been said in praise of that virtue by Plato and Aristotle. But it was a principle of the sect to which Carneades belonged that every affirmative proposition, however strongly supported, might be denied with equal plausibility. Accordingly, his second discourse was entirely devoted to upsetting the conclusions advocated in the first. Transporting the whole question, as would seem, from a private to a public point of view, he attempted to show, from the different standards prevailing in different countries, that there was no such thing as an immutable rule of right; and also that the greatest and most successful States had profited most by unscrupulous aggressions on their weaker neighbours—his most telling illustrations being drawn from the history of the Romans themselves. Then, descending once more to private life, the sceptical lecturer expatiated on the frequency of those cases in which justice is opposed to self-interest, and the folly of sacrificing one’s own advantage to that of another. ‘Suppose a good man has a runaway slave or an unhealthy house to sell, will he inform the buyer of their deficiencies, or will he conceal them? In the one case he will be a fool, in the other case he will be unjust. Again, justice forbids us to take away the life or property of another. But in a shipwreck, will not the just man try to save his life at another’s expense by seizing the plank of which some weaker person than himself has got hold—especially if they are alone on the sea together? If he is wise he will do so, for to act otherwise would be to sacrifice his life. So also, in flying before the enemy, will he not dispossess a wounded comrade of his horse, in order to mount and escape on it himself? Here, again, justice is incompatible with self-preservation—that is to say, with wisdom!‘213
At the time when Carneades delivered his lectures, the morality of Rome resembled that of Sparta during her great conflict with Athens, as characterised by one of the speakers in the Melian Dialogue. Scrupulously honourable in their dealings with one another, in their dealings with foreign nations her citizens notoriously identified justice with what was agreeable or advantageous to themselves. The arguments of the Academic philosopher must, therefore, have been doubly annoying to the leaders of the State, as a satire on its public policy and as a source of danger to the integrity of its private life. In this respect, old Cato was a type of the whole race. In all transactions with his fellow-citizens, and in every office undertaken on behalf of the community, his honesty was such that it became proverbial. But his absolute disregard of international justice has become equally proverbial through the famous advice, reiterated on every possible occasion, that an unoffending and unwarlike city should be destroyed, lest its existence should at some future time become a source of uneasiness to the mistress of the world. Perhaps it was a secret consciousness of his own inconsistency which prevented him from directly proposing that Carneades should not be allowed to continue his lectures. At any rate, the ex-Censor contented himself with moving that the business on which the Athenian envoys had come should be at once concluded, that they might return to their classes at Athens, leaving the youth of Rome to seek instruction as before from the wise conversation and example of her public men.214 We are not told whether his speech on this occasion wound up with the usual formula, caeterum, Patres Conscripti, sententia mea est Carthaginem esse delendam; but as it is stated that from the year 175 to the end of his life, he never made a motion in the Senate that was not terminated by those words, we are entitled to assume that he did not omit them in the present instance. If so, the effect must have been singularly grotesque; although, perhaps, less so than if attention had been drawn to the customary phrase by its unexpected absence. At any rate, Carneades had an opportunity of carrying back one more illustration of ethical inconsistency wherewith to enliven his lectures on the ‘vanity of dogmatising’ and the absolute equilibrium of contradictory opinions.
It has been mentioned that Carneades was the head of the Academic school. In that capacity, he was the lineal inheritor of Plato’s teaching. Yet a public apology for injustice, even when balanced by a previous panegyric on its opposite, might seem to be of all lessons the most alien from Platonism; and in a State governed by Plato’s own laws, it would certainly have been punishable with death. To explain this anomaly is to relate the history of Greek scepticism, which is what we shall now attempt to do.
In modern parlance, the word scepticism is often used to denote absolute unbelief. This, however, is a misapplication; and, properly speaking, it should be reserved, as it was by the Greeks, for those cases in which belief is simply withheld, or in which, as its etymology implies, the mental state connoted is a desire to consider of the matter before coming to a decision. But, of course, there are occasions when, either from prudence or politeness, absolute rejection of a proposition is veiled under the appearance of simple indecision or of a demand for further evidence; and at a time when to believe in certain theological dogmas was either dangerous or discreditable, the name sceptic may have been accepted on all hands as a convenient euphemism in speaking about persons who did not doubt, but denied them altogether. Again, taken in its original sense, the name sceptic is applicable to two entirely different, or rather diametrically opposite classes. The true philosopher is more slow to believe than other men, because he is better acquainted than they are with the rules of evidence, and with the apparently strong claims on our belief often possessed by propositions known to be false. To that extent, all philosophers are sceptics, and are rightly regarded as such by the vulgar; although their acceptance of many conclusions which the unlearned reject without examination, has the contrary effect of giving them a reputation for extraordinary credulity or even insanity. And this leads us to another aspect of scepticism—an aspect under which, so far from being an element of philosophy, it is one of the most dangerous enemies that philosophy has to face. Instead of regarding the difficulties which beset the path of enquiry as a warning against premature conclusions, and a stimulus to more careful research, it is possible to make them a pretext for abandoning enquiry altogether. And it is also possible to regard the divergent answers given by different thinkers to the same problem, not as materials for comparison, selection or combination, nor even as indications of the various directions in which a solution is not to be sought, but as a proof that the problem altogether passes the power of human reason to solve.
Were this intellectual despondency to issue in a permanent suspense of judgment, it would be bad enough; but practically its consequences are of a much more mischievous character. The human mind is so constituted that it must either go forward or fall back; in no case can it stand still. Accordingly, the lazy sceptic almost always ends by conforming to the established creeds and customs of his age or of the society in which he lives; thus strengthening the hands of authority in its conflict with the more energetic or courageous enquirers, whose object is to discover, by the unaided efforts of reason, some new and positive principle either of action or of belief. And the guardians of orthodoxy are so well aware of the profit to be reaped from this alliance that, when debarred from putting down their opponents by law or by public opinion, they anxiously foster false scepticism where it is already rampant, and endeavour to create it where it does not exist. Sometimes disinterested morality is the object of their attack, and at other times the foundations of inductive science. Their favourite formula is that whatever objections may be urged against their own doctrines, others equally strong may be urged against the results of free thought; whereas the truth is that such objections, being applicable to all systems alike, exactly balance one another, leaving the special arguments against irrationalism to tell with as much force as before. And they also lay great stress on the internal dissensions of their assailants—dissensions which only bring out into more vivid relief the one point on which all are agreed, that, whatever else may be true, the traditional opinions are demonstrably false.
As might be expected from the immense exuberance of their intellectual life, we find every kind of scepticism represented among the Greeks; and, as with their other philosophical tendencies, there is evidence of its existence previous to or independent of scientific speculation. Their very religion, though burdened with an enormous mass of fictitious legends, shows a certain unwillingness to transgress the more obvious laws of nature, not noticeable in the traditions of kindred or neighbouring races. Its tendency is rather to imagine supernatural causes for natural events, or to read a divine meaning into accidental occurrences, than to introduce impossibilities into the ordinary course of history. And some of its most marvellous stories are told in such a manner that the incredulous satire with which they were originally received is, by a beautiful play of irony, worked into the very texture of the narrative itself. For example, the Greeks were especially disinclined to believe that one of the lower animals could speak with a human voice, or that a dead man could be brought back to life—contradicted as both suppositions were by the facts of universal experience. So when the horse Xanthus replies to his master’s reproaches, Homer adds that his voice was arrested by the Erinyes—that is to say, by the laws of nature; and we may suspect that nothing more is intended by his speech than the interpretation which Achilles would spontaneously put on the mute and pathetic gaze of the faithful steed. And when, to illustrate the wondrous medical skill of Asclêpius, it is related that at last he succeeded in restoring a dead man to life, the story adds that for this impious deed both the healer and his patient were immediately transfixed by a thunderbolt from heaven.215 Another impossibility is to predict with any certainty the future fate of individuals, and here also—as has been already observed in a different connexion216—the Greeks showed their extreme scepticism with regard to any alleged contravention of a natural law, under the transparent disguise of stories about persons whom ambiguous predictions had lured to their fall.
It is even doubtful how far the Greek poets believed in the personality of their gods, or, what comes to the same thing, in their detachment from the natural objects in which a divine power was supposed to be embodied. Such a detachment is most completely realised when they are assembled in an Olympian council; but, as Hegel has somewhere observed, Homer never brings his gods together in this manner without presenting them in a ridiculous light—that is to say, without hinting that their existence must not be taken quite in earnest. And the existence of disembodied spirits seems to be similarly conceived by the great epic master. The life of the souls in Hades is not a continuance but a memory and a reflection of their life on earth. The scornful reply of Achilles to the congratulations of Odysseus implies, as it were, the consciousness of his own nonentity. By no other device could the irony of the whole situation, the worthlessness of a merely subjective immortality, be made so poignantly apparent.217
The characters in Homer are marked by this incredulous disposition in direct proportion to their general wisdom. When Agamemnon relates his dream to the assembled chiefs, Nestor dryly observes that if anyone of less authority had told them such a story they would have immediately rejected it as untrue. Hector’s outspoken contempt for augury is well known; and his indifference to the dying words of Patroclus is equally characteristic. In the Odyssey, Alcinous pointedly distinguishes his guest from the common run of travellers, whose words deserve no credit. That Telemachus should tell who is his father, with the uncomplimentary reservation that he has only his mother’s word for it, is evidently meant as a proof of the young man’s precocious shrewdness; and it is with the utmost difficulty that Penelope herself is persuaded of her husband’s identity. So in the Agamemnon of Aeschylus, nothing less than the report of an eye-witness will convince the Chorus of old men that Troy has really fallen.218 Finally, to complete the list of examples afforded independently of philosophical reflection, Herodotus repeatedly expresses disbelief in the stories told him, or, what is more remarkable, holds his judgment in suspense with regard to their veracity.
Scepticism, as a philosophical principle, is alien from early Greek thought; but it is pervaded by a negative tendency exhibited in four different directions, all converging towards the later attitude of suspensive doubt. There are sharp criticisms on the popular mythology; there are protests against the ascription of reality to sensible appearances; there are contemptuous references on the part of some philosophers to the opinions held by others; and there are occasional lamentations over the difficulty of getting at any truth at all. The importance, however, of these last utterances has been considerably exaggerated both in ancient and modern times. For, in some instances, they are attributable solely to the distrust of sense-perception, and in others they seem to express nothing more than a passing mood against which we must set the dogmatic conclusions elsewhere enunciated with perfect confidence by the same thinkers.219 At the same time, we have to note, as an illustration of the standing connexion between theological belief and that kind of scepticism which is shown by distrust in man’s power of discovering the truth for himself, that the strongest expressions of such a distrust are to be found in the two most religious of the pre-Socratic thinkers, Xenophanes and Empedocles.
A new period begins with the Greek Humanists. We use this term in preference to that of Sophists, because, as has been shown, in specially dealing with the subject, half the teachers known under the latter denomination made it their business to popularise physical science and to apply it to morality, while the other half struck out an entirely different line, and founded their educational system on the express rejection of such investigations; their method being, in this respect, foreshadowed by the greatest poet of the age, who concentrates all his attention on the workings of the human mind, and followed by its greatest historian, with whom a similar study takes the place occupied by geography and natural history in the work of Herodotus. This absorption in human interests was unfavourable alike to the objects and to the methods of previous enquiry: to the former, as a diversion from the new studies; to the latter, as inconsistent with the flexibility and many-sidedness of conscious mind. Hence the true father of philosophical scepticism was Protagoras. With him, for the first time, we find full expression given to the proper sceptical attitude, which is one of suspense and indifference as opposed to absolute denial. He does not undertake to say whether the gods exist or not. He regards the real essence of Nature as unknowable, on account of the relativity which characterises all sensible impressions. And wherever opinions are divided, he undertakes to provide equally strong arguments for both sides of the question. He also anticipates the two principal tendencies exhibited by all future scepticism in its relation to practice. One is its devotion to humanity, under the double form of exclusive attention to human interests, and great mildness in the treatment of human beings. The other is a disposition to take custom and public opinion, rather than any physical or metaphysical law, for the standard and sanction of morality. Such scepticism might for the moment be hostile to religion; but a reconciliation was likely to be soon effected between them.
The famous theses of Gorgias were quoted in a former chapter as an illustration of the tactics pursued by Greek Humanism in its controversy with physical science. They must be noticed again in the present connexion, on account of their bearing on the development of scepticism, and as having inaugurated a method of reasoning often employed in subsequent attacks, directed, not against the whole of knowledge, but against particular parts of it. The scepticism of Protagoras rested on the assumption that there is an external reality from the reaction of which with mind all our perceptions proceed. Neither of these two factors can be known apart from the other, and as both are in a constant flux, our knowledge of the resulting compound at one time does not show what it has been or will be at another time. But Gorgias altogether denied the existence of any objective reality; and he attempted to disprove it by an analytical instead of a synthetic argument, laying down a series of disjunctive propositions, and upsetting the different alternatives in succession. Existence must be either something or nothing, or both together; and if something, it must be either finite or infinite, or both, and either one or many, or both. His argument against an infinite existence is altogether futile; but it serves to illustrate the undeveloped state of reflection at that period. The eternity of the world is confounded with its unlimited extension in space: and this hypothesis, again, is met by the transparent quibble that the world, not being in any one place, must be nowhere or not at all. And the alternative that the world has not always existed is refuted by the unproved assumption, which, apparently, no Greek philosopher ever thought of disputing, that nothing can begin without being caused by something else. Still, however contemptible such reasonings may seem, it is obvious that in them we have the first crude form of the famous antinomies by which Kant long afterwards sought to prove the impossibility of a world existing in space and time apart from a percipient subject, and which have since been used to establish in a more general way the unknowability of existence as such. It will also be observed that the sceptical arguments respectively derived from the relativity of thought and from the contradictions inherent in its ultimate products are run together by modern agnostics. But no reason that we can remember has ever been given to show that an idea is necessarily subjective because it is self-contradictory.
The second thesis of Gorgias was that, even granting the world to exist, it could not possibly be known. Here the reasoning is unexpectedly weak. Because all thoughts do not represent facts,—as, for example, our ideas of impossible combinations, like chariots running over the sea,—it is assumed that none do. But the problem how to distinguish between true and false ideas was raised, and it was round this that the fiercest battle between dogmatists and sceptics subsequently raged. And in the complete convertibility of consciousness and reality postulated by Gorgias, we may find the suggestion of a point sometimes overlooked in the automatist controversy—namely, that the impossibility, if any, of our acting on the material world reciprocally involves the impossibility of its acting on us, in so far as we are conscious beings. If thought cannot be translated into movement, neither can movement be translated into thought.
The third thesis maintains that, granting the world to exist and to be knowable, one man cannot communicate his knowledge to another; for, the different classes of sensations being heterogeneous, a visual or tactual impression on our consciousness cannot be conveyed by an auditory impression on the consciousness of someone else. This difficulty has been completely overcome by the subsequent progress of thought. We cannot, it is true, directly communicate more than a few sensations to one another; but by producing one we may call up others with which it has become associated through previous experience. And the great bulk of our knowledge has been analysed into relations of co-existence, succession, and resemblance, which are quite independent of the particular symbols employed to transmit them from one mind to another.220
The scepticism of Aristippus and the Cyrenaics mediated between the views of Protagoras and those of Gorgias, while marking an advance on both. According to this school, we know nothing beyond our own feelings, and it must be left undecided whether they are caused by an external reality or not. Nor can the feelings of one individual justify us in reasoning to the existence of similar feelings in the mind of another individual.221 It might be objected that the arguments advanced in support of the latter assertion are suicidal, for they are derived from the abnormal states of consciousness accompanying particular diseases, or else from the divergences of taste exhibited by different individuals even when in good health,—an apparent admission that we are sufficiently well acquainted with the phenomena in question to institute a comparison between them, which, by hypothesis, is impossible. And this is, in fact, the method by which Mr. Herbert Spencer has endeavoured to upset the whole theory of subjective idealism, as involving at every step an assumption of the very realities that it professes to deny. But the Cyrenaic and the modern idealist have a perfect right to show that the assumptions of their adversaries are self-contradictory; and the readiest way of so doing is to reason from them as if they were true. The real answer to that extreme form of idealism which denies the possibility of making known our feelings to each other is that, our bodies being similarly constructed and responding to similar impressions by similar manifestations, I have the same sort of warrant for assuming that your states of consciousness are like mine that I have for assuming you to exist at all. The inference must, of course, be surrounded by proper precautions, such as are seldom used by unscientific reasoners. We must make sure that the structure is the same and that the excitement is the same, or that their differences, if any, are insignificant, before we can attribute the same value to the same manifestations of feeling on the part of different persons; but that this can be done, at least in the case of the elementary sensations, is shown by the easy detection of such anomalies as colour-blindness where they exist.
With Socrates and Plato, scepticism exhibits itself under two new aspects: as an accompaniment of religious belief, and as an element of constructive thought. Thus they represent both the good and the bad side of this tendency: the aspect under which it is a help, and the aspect under which it is a hindrance to scientific investigation. With both philosophers, however, the restriction or negation of human knowledge was a consequence rather than a cause of their theological convictions; nor do they seem to have appreciated its value as a weapon in the controversy with religious unbelief. When Socrates represented the irreconcilable divergence in the explanations of Nature offered by previous thinkers as a sufficient condemnation of their several pretensions, he did not set this fact against the arguments by which a Xenophanes had similarly endeavoured to overthrow the popular mythology; but he looked on it as a fatal consequence of their insane presumption in meddling with the secrets of the gods. On one occasion only, when explaining to Euthydêmus that the invisibility of the gods is no reason for doubting their existence, he argues, somewhat in Butler’s style, that our own minds, whose existence we cannot doubt, are equally invisible.222 And the Platonic Socrates makes it his business to demonstrate the universality of human ignorance, not as a caution against dogmatic unbelief, but as a glorification of the divine knowledge; though how we come to know that there is any such knowledge he leaves utterly unexplained.
In Plato’s Parmenides we have to note the germ of a new dialectic. There it is suggested that we may overcome the difficulties attending a particular theory—in this instance the theory of self-existing ideas—by considering how much greater are the difficulties which would ensue on its rejection. The arguments advanced by Zeno the Eleatic against the reality of motion are mentioned as a case in point; and Plato proceeds to illustrate his proposed method by showing what consequences respectively follow if we first assume the existence, and then the non-existence of the One; but the whole analysis seems valueless for its immediate purpose, since the resulting impossibilities on either side are left exactly balanced; and Plato does not, like some modern metaphysicians, call in our affections to decide the controversy.
The method by which Plato eventually found his way out of the sceptical difficulty, was to transform it from a subjective law of thought into an objective law of things. Adopting the Heracleitean physics as a sufficient explanation of the material world, he conceived, at a comparatively early period of his mental evolution, that the fallaciousness of sense-impressions is due, not to the senses themselves, but to the instability of the phenomena with which they deal; and afterwards, on discovering that the interpretation of ideal relations was subject to similar perplexities, he assumed that, in their case also, the contradiction arises from a combination of Being with not-Being determining whatever differences prevail among the ultimate elements of things. And, finally, like Empedocles, he solved the problem of cognition by establishing a parallel between the human soul and the universe as a whole; the circles of the Same and the Other being united in the celestial orbits and also in the mechanism of the brain.223
It was by an analogous, though, of course, far more complicated and ingenious adjustment, that Hegel sought to overcome the agnosticism which Kant professed to have founded on a basis of irrefragable proof. With both philosophers, however, the sceptical principle was celebrating its supreme triumph at the moment of its fancied overthrow. The dogmatism of doubt could go no further than to resolve the whole chain of existence into a succession of mutually contradictory ideas.
If the synthesis of affirmation and negation cannot profitably be used to explain the origin of things in themselves, it has a real and very important function when limited to the subjective sphere, to the philosophy of practice and of belief. It was so employed by Socrates, and, on a much greater scale, by Plato himself. To consider every proposition from opposite points of view, and to challenge the claim of every existing custom on our respect, was a proceeding first instituted by the master, and carried out by the disciple in a manner which has made his investigations a model for every future enquirer. Something of their spirit was inherited by Aristotle; but, except in his logical treatises, it was overborne by the demands of a pre-eminently dogmatic and systematising genius. In criticising the theories of his predecessors, he has abundantly illustrated the power of dialectic, and he has enumerated its resources with conscientious completeness; but he has not verified his own conclusions by subjecting them to this formidable testing apparatus.
Meanwhile the scepticism of Protagoras had not been entirely absorbed into the systems of his rivals, but continued to exist as an independent tradition, or in association with a simpler philosophy. The famous school of Megara, about which, unfortunately, we have received very little direct information, was nominally a development of the Socratic teaching on its logical side, as the Cynic and Cyrenaic schools were on its ethical side, but like them also, it seems to have a more real connexion with the great impulse previously given to speculation by the Sophists. At any rate, we chiefly hear of the Megarians as having denied the possibility of definition, to which Socrates attached so much importance, and as framing questions not susceptible of a categorical answer,—an evident satire on the Socratic method of eliciting the truth by cross-examination.224 What they really derived from Socrates seems to have been his mental concentration and independence of external circumstances. Here they closely resembled the Cynics, as also in their contempt for formal logic; but while Antisthenes found a sanction for his indifference and impassivity in the order of nature, their chief representative, Stilpo, achieved the same result by pushing the sceptical principle to consequences from which even the Cyrenaics would have shrunk. Denying the possibility of attaching a predicate to a subject, he seems, in like manner, to have isolated the mind from what are called its affections, or, at least, to have made this isolation his ideal of the good. Even the Stoics did not go to such a length; and Seneca distinguishes himself from the followers of Stilpo by saying, ‘Our sage feels trouble while he overcomes it, whereas theirs does not feel it at all.’225
So far, the sceptical theory had been put forward after a somewhat fragmentary fashion, and in strict dependence on the previous development of dogmatic philosophy. With the Humanists it had taken the form of an attack on physical science; with the Megarians, of a criticism on the Socratic dialectic; with both, it had been pushed to the length of an absolute negation, logically not more defensible than the affirmations to which it was opposed. What remained was that, after being consistently formulated, its results should be exhibited in their systematic bearing on the practical interests of mankind. The twofold task was accomplished by Pyrrho, whose name has accordingly continued to be associated, even in modern times, with the profession of universal doubt. This remarkable man was a native of Elis, where a branch of the Megarian school had at one time established itself; and it seems likely that the determining impulse of his life was, directly or indirectly, derived from Stilpo’s teaching. A contemporary of Alexander the Great, he accompanied the Macedonian army on its march to India, subsequently returning to his native city, where he died at an advanced age, about 275 B.C. The absurd stories about his indifference to material obstacles when out walking have been already mentioned in a former chapter, and are sufficiently refuted by the circumstances just related. The citizens of Elis are said to have shown their respect for the philosopher by exempting him from taxation, appointing him their chief priest—no inappropriate office for a sceptic of the true type—and honouring his memory with a statue, which was still pointed out to sightseers in the time of Pausanias.226
Pyrrho, who probably no more believed in books than in anything else, never committed his opinions to writing; and what we know of them is derived from the reports of his disciples, which, again, are only preserved in a very incomplete form by the compilers of the empire. According to these, Pyrrho began by declaring that the philosophic problem might be summed up in the three following questions: ‘What is the nature of things? What should be our relation to them? What is the practical consequence of this determination?’ Of its kind, this statement is probably the best ever framed, and might be accepted with equal readiness by every school of thought. But the scepticism of Pyrrho at once reveals itself in his answer to the first question. We know nothing about things in themselves. Every assertion made respecting them is liable to be contradicted, and neither of the two opposing propositions deserves more credence than the other. The considerations by which Pyrrho attempts to establish this proposition were probably suggested by the systems of Plato and Aristotle. The only possible avenues of communication with the external world are, he tells us, sense and reason. Of these the former was so universally discredited that he seems to have regarded any elaborate refutation of its claims as superfluous. What we perceive by our senses is the appearance, not the reality of things. This is exactly what the Cyrenaics had already maintained. The inadequacy of reason is proved by a more original method. Had men any settled principles of judgment, they would agree on questions of conduct, for it is with regard to these that they are best informed, whereas the great variety of laws and customs shows that the exact opposite is true. They are more hopelessly divided on points of morality than on any other.227 It will be remembered that Pyrrho’s fellow-townsman, Hippias, had, about a hundred years earlier, founded his theory of Natural Law on the arbitrary and variable character of custom. The result of combining his principles with those professed by Protagoras and Gorgias was to establish complete moral scepticism; but it would be a mistake to suppose that moral distinctions had no value for him personally, or that they were neglected in his public teaching.
Timon, a celebrated disciple of Pyrrho, added another and, from the speculative point of view, a much more powerful argument, which, however, may equally have been borrowed from the master’s lectures. Readers of the Posterior Analytics will remember how strongly Aristotle dwells on the necessity of starting with first principles which are self-evidently true. The chain of demonstration must have something to hang on, it cannot be carried back ad infinitum. Now, Timon would not admit of such a thing as first principles. Every assumption, he says, must rest on some previous assumption, and as this process cannot be continued for ever, there can be no demonstration at all. This became a very favourite weapon with the later Sceptics, and, still at the suggestion of Aristotle, they added the further ‘trope’ of compelling their adversaries to choose between going back ad infinitum and reasoning in a circle—in other words, proving the premises by means of the conclusion. Modern science would not feel much appalled by the sceptical dilemma. Its actual first principles are only provisionally assumed as ultimate, and it is impossible for us to tell how much farther their analysis may be pursued; while, again, their validity is guaranteed by the circular process of showing that the consequences deduced from them agree with the facts of experience. But as against those modern philosophers who, in adherence to the Aristotelian tradition, still seek to base their systems on first principles independent of any individual experience, the sceptical argument is unanswerable, and has even been strengthened by the progress of knowledge. To this day, thinkers of different schools cannot agree about the foundations of belief, and what to one seems self-evidently true, is to another either conceivably or actually false. To Mr. Herbert Spencer the persistence of force is a necessary truth; to Prof. Stanley Jevons its creation is a perfectly possible contingency; while to others, again, the whole conception of force, as understood by Mr. Spencer, is so absolutely unmeaning that they would decline to entertain any proposition about the invariability of the objective reality which it is supposed to represent. And when the à priori dogmatist affects to treat the negations of his opponents as something that they do not think, but only think they think, they may, with perfect fairness, attribute his rejection of their beliefs—as, for example, free-will—to a similar subjective illusion. Moreover, the pure experimentalists can point to a circumstance not foreseen by the ancient sceptics, which is that propositions once generally regarded as incontrovertible by thinking men, are now as generally abandoned by them.
Having proved, to his satisfaction, that the nature of things is unknowable, Pyrrho proceeds to deal with the two remaining heads of the philosophic problem. To the question what should be our relation to a universe which we cannot reach, the answer is, naturally, one of total indifference. And the advantage to be derived from this attitude is, he tells us, that we shall secure the complete imperturbability wherein true happiness consists. The sceptical philosophy does not agree with Stilpo in denying the reality of actual and immediate annoyances, for it denies nothing; but it professes to dispel that very large amount of unhappiness which arises from the pursuit of fancied goods and the expectation of future calamities. In respect to the latter, what Pyrrho sought was to arrive by the exercise of reasoning at the tranquillity which unreasoning animals naturally enjoy. Thus, we are told that, when out at sea in a storm, he called the attention of the terrified passengers to a little pig which was quietly feeding in spite of the danger, and taught them that the wise man should attain to a similar kind of composure.
Various other anecdotes of more or less doubtful authenticity are related, showing that the philosopher could generally, though not always, act up to his own ideal of indifference. He lived with his sister, who was a midwife by profession, and patiently submitted to the household drudgery which she unsparingly imposed on him. Once, however, she succeeded in goading him into a passion; and on being rather inopportunely reminded of his professed principles by a bystander, the sceptic tartly replied that a wretched woman like that was no fit subject for a display of philosophical indifference. On another occasion, when taunted for losing his self-possession at the attack of a furious dog, he observed, with truth, that, after all, philosophers are human beings.228
Thus we find Pyrrho competing with the dogmatists as a practical moralist, and offering to secure the inward tranquillity at which they too aimed by an easier method than theirs. The last eminent representative of the sceptical school, Sextus Empiricus, illustrates its pretensions in this respect by the well-known story of Apelles, who, after vainly endeavouring to paint the foam on a horse’s mouth, took the sponge which he used to wipe his easel, and threw it at the picture in vexation. The mixture of colours thus accidentally applied produced the exact effect which he desired, but at which no calculation could arrive. In like manner, says Sextus, the confusion of universal doubt accidentally resulted in the imperturbability which accompanies suspense of judgment as surely as a body is followed by its shadow.229 There was, however, no accident about the matter at all. The abandonment of those studies which related to the external world was a consequence of the ever-increasing attention paid to human interests, and that these could be best consulted by complete detachment from outward circumstances, was a conclusion inevitably suggested by the negative or antithetical moment of Greek thought. Hence, while the individualistic and apathetic tendencies of the age were shared by every philosophical school, they had a closer logical connexion with the idealistic than with the naturalistic method; and so it is among the successors of Protagoras that we find them developed with the greatest distinctness; while their incorporation with Stoicism imposed a self-contradictory strain on that system which it never succeeded in shaking off. Epicureanism occupied a position midway between the two extremes; and from this point of view, we shall be better able to understand both its inherent weakness as compared with the other ancient philosophies, and the admiration which it has attracted from opposite quarters in recent years. To some it is most interesting as a revelation of law in Nature, to others as a message of deliverance to man—not merely a deliverance from ignorance and passion, such as its rivals had promised, but from all established systems, whether religious, political, or scientific. And unquestionably Epicurus did endeavour to combine both points of view in his theory of life. In seeking to base morality on a knowledge of natural law he resembles the Stoics. In his attacks on fatalism, in his refusal to be bound down by a rigorously scientific explanation of phenomena, in his failure to recognise the unity and power of Nature, and in his preference of sense to reason, he partially reproduces the negative side of Scepticism; in his identification of happiness with the tranquil and imperturbable self-possession of mind, in his mild humanism, and in his compliance with the established religion of the land, he entirely reproduces its positive ethical teaching. On the other hand, the two sides of his philosophy, so far from completing, interfere with and mar one another. Emancipation from the outward world would have been far more effectually obtained by a total rejection of physical science than by the construction of a theory whose details were, on any scientific principles, demonstrably untrue. The appeal to natural instinct as an argument for hedonism would, consistently followed out, have led to one of two conclusions, either of which is incompatible with the principle that imperturbability is the highest good. If natural instinct, as manifested by brutes, by children, and by savages, be the one sure guide of action, then Callicles was right, and the habitual indulgence of passion is wiser than its systematic restraint. But if Nature is to be studied on a more specific and discriminating plan, if there are human as distinguished from merely animal impulses, and if the higher development of these should be our rule of life, then Plato and Aristotle and the Stoics were right, and the rational faculties should be cultivated for their own sake, not because of the immunity from superstitious terrors which they secure. And we may add that the attendance on public worship practised by Epicurus agreed much better with the sceptical suspense of judgment touching divine providence than with its absolute negation, whether accompanied or not by a belief in gods who are indifferent to sacrifice and prayer.
It was, no doubt, for these and similar reasons that all the most vigorous intellects of Hellas ranged themselves either on the Stoic or on the Sceptic side, leaving the halfhearted compromise of Epicurus to those who could not think out any one theory consistently, or who, like the Romans at first, were not acquainted with any system but his. Henceforth, during a period of some centuries, the whole philosophic movement is determined by the interaction of these two fundamental forces. The first effect of their conflict was to impose on Scepticism an important modification, illustrating its essentially parasitic character. We have seen it, as a general tendency of the Greek mind, clinging to the very texture of mythology, accompanying the earliest systematic compilation of facts, aiding the humanistic attacks on physical science, associated with the first great religious reaction, operating as the dialectic of dialectic itself, and finally assuming the form of a shadowy morality, in rivalry with and imitation of ethical systems based on a positive and substantial doctrine. We have now to trace its metamorphosis into a critical system extending its ramifications in parallelism with the immense dogmatic structure of Stoicism, and simultaneously endeavouring to reach the same practical results by a more elastic adaptation to the infirmities of human reason and the uncertainties of sensible experience. As such, we shall also have to study its influence over the most plastic of Roman intellects, the great orator in whose writings Greek philosophy was reclothed with something of its ancient charm, so that many who were debarred from admission to the groves and porticoes of Athens have caught an echo of the high debates which once stirred their recesses, as they trod the shady slopes of Tusculum under his visionary guidance, or followed his searching eyes over the blue waters to Pompeii, while he reasoned on mind and its object, on sense and knowledge, on doubt and certainty, with Lucullus and Hortensius, on the sunlight Baian shore. It is the history of the New Academy that we shall now proceed to trace.
When we last had occasion to speak of the Platonic school, it was represented by Polemo, one of the teachers from whose lessons Zeno the Stoic seems to have compiled his system. Under his superintendence, Platonism had completely abandoned the metaphysical traditions of its founder. Physics and dialectics had already been absorbed by Aristotelianism. Mathematics had passed into the hands of experts. Nothing remained but the theory of ethics; and, as an ethical teacher, Polemo was only distinguished from the Cynics by the elegance and moderation of his tone. Even this narrow standing-ground became untenable when exposed to the formidable competition of Stoicism. The precept, Follow Nature, borrowed by the new philosophy from Polemo, acquired a far deeper significance than he could give it, when viewed in the light of an elaborate physical system showing what Nature was, and whither her guidance led. But stone after stone had been removed from the Platonic superstructure and built into the walls of other edifices, only to bring its original foundation the more prominently into sight. This was the initial doubt of Socrates, widened into the confession of universal ignorance attributed to him by Plato in the Apologia. Only by returning to the exclusively critical attitude with which its founder had begun could the Academy hope to exercise any influence on the subsequent course of Greek speculation. And it was also necessary that the agnostic standpoint should be taken much more in earnest by its new representatives than by Socrates or Plato. With them it had been merely the preparation for a dogmatism even more self-confident than that of the masters against whom they fought; but if in their time such a change of front might seem compatible with the retention of their old strongholds, matters now stood on a widely different footing. Experience had shown that the purely critical position could not be abandoned without falling back on some one or other of the old philosophies, or advancing pretensions inconsistent with the dialectic which had been illustrated by their overthrow. The course marked out for Plato’s successors by the necessities of thought might have been less evident had not Pyrrhonism suddenly revealed to them where their opportunities lay, and at the same time, by its extinction as an independent school, allowed them to step into the vacant place.
It was at this juncture that the voluntary withdrawal of an older fellow-pupil placed Arcesilaus at the head of the Academy. The date of his accession is not given, but we are told that he died 241 or 240 B.C. in the seventy-fifth year of his age. He must, therefore, have flourished a generation later than Zeno and Epicurus. Accomplished, witty, and generous, his life is described by some as considerably less austere than that of the excellent nonentities whom he succeeded. Yet its general goodness was testified to by no less an authority than his contemporary, the noble Stoic, Cleanthes. ‘Do not blame Arcesilaus,’ exclaimed the latter to an unfriendly critic; ‘if he denies duty in his words, he affirms it in his deeds.’ ‘You don’t flatter me,‘ observed Arcesilaus. ‘It is flattering you,’ rejoined Cleanthes, ‘to say that your actions belie your words.’230 It might be inferred from this anecdote that the scepticism of the new teacher, like that of Carneades after him, was occasionally exercised on moral distinctions, which, as then defined and deduced, were assuredly open to very serious criticism. Even so, in following the conventional standard of the age, he would have been acting in perfect consistency with the principles of his school. But, as a matter of fact, his attacks seem to have been exclusively aimed at the Stoic criterion of certainty. We have touched on this difficult subject in a former chapter, but the present seems a more favourable opportunity for setting it forth in proper detail.
The Stoics held, as Mr. Herbert Spencer, who resembles them in so many respects, now holds, that all knowledge is ultimately produced by the action of the object on the subject. Being convinced, however, that each single perception, as such, is fallible, they sought for the criterion of certainty in the repetition and combination of individual impressions; and, again like Mr. Spencer, but also in complete accordance with their dynamic theory of Nature, they estimated the validity of a belief by the degree of tenacity with which it is held. The various stages of assurance were carefully distinguished and arranged in an ascending series. First came simple perception, then simple assent, thirdly, comprehension, and finally demonstrative science. These mental acts were respectively typified by extending the forefinger, by bending it as in the gesture of beckoning, by clenching the fist, and by placing it, thus clenched, in the grasp of the other hand. From another point of view, they defined a true conviction as that which can only be produced by the action of a corresponding real object on the mind. This theory was complicated still further by the Stoic interpretation of judgment as a voluntary act; by the ethical significance which it consequently received; and by the concentration of all wisdom in the person of an ideal sage. The unreserved bestowal of belief is a practical postulate dictated by the necessities of life; but only he who knows what those necessities are, in other words only the wise man, knows when the postulate is to be enforced. In short, the criterion of your being right is your conviction that you are right, and this conviction, if you really possess it, is a sufficient witness to its own veracity. Or again, it is the nature of man to act rightly, and he cannot do so unless he has right beliefs, confirmed and clinched by the consciousness that they are right.
Arcesilaus left no writings, and his criticisms on the Stoic theory, as reported by Cicero and Sextus Empiricus, have a somewhat unsatisfactory appearance. By what we can make out, he seems to have insisted on the infallibility of the wise man to a much greater extent than the Stoics themselves, not allowing that there was any class of judgments in which he was liable to be mistaken. But just as the Stoics were obliged to accept suicide as an indispensable safeguard for the inviolability of their personal dignity and happiness, so also Arcesilaus had recourse to a kind of intellectual suicide for the purpose of securing immunity from error. The only way, according to him, in which the sage can make sure of never being mistaken is never to be certain about anything. For, granting that every mental representation is produced by a corresponding object in the external world, still different objects are connected by such a number of insensible gradations that the impressions produced by them are virtually indistinguishable from one another; while a fertile source of illusions also exists in the diversity of impressions produced by the same object acting on different senses and at different times. Moreover, the Stoics themselves admitted that the sage might form a mistaken opinion; it was only for his convictions that they claimed unerring accuracy, each of the two—opinion and conviction—being the product of a distinct intellectual energy. Here again, Arcesilaus employed his method of infinitesimal transitions, refusing to admit that the various cognitive faculties could be separated by any hard and fast line; especially as, according to the theory then held by all parties, and by none more strongly than the Stoics, intellectual conceptions are derived exclusively from the data of sense and imagination. We can see that the logic of Scepticism is, equally with that of the other Greek systems, determined by the three fundamental moments of Greek thought. There is first the careful circumscription of certainty; then there is the mediating process by which it is insensibly connected with error; and, lastly, as a result of this process, there is the antithetical opposition of a negative to an affirmative proposition on every possible subject of mental representation.231
To the objection that his suspensive attitude would render action impossible, Arcesilaus replied that any mental representation was sufficient to set the will in motion; and that, in choosing between different courses, probability was the most rational means of determination. But the task of reducing probable evidence to a system was reserved for a still abler dialectician, who did not appear on the scene until a century after his time. Arcesilaus is commonly called the founder of the Middle, Carneades the founder of the New Academy. The distinction is, however, purely nominal. Carneades founded nothing. His principles were identical with those of his predecessor; and his claim to be considered the greatest of the Greek sceptics is due to his having given those principles a wider application and a more systematic development. The Stoics regarded it as a special dispensation of providence that Chrysippus, the organising genius of their school, should have come between its two most formidable opponents, being thus placed in a position to answer the objections of the one and to refute by anticipation those of the other.232 It might seem to less prejudiced observers that the thinker whose cause benefited most by this arrangement was Carneades. Parodying a well-known iambic, he used to say:
‘Without Chrysippus I should not have been.’233
And, in fact, it was by a close study of that writer’s voluminous treatises that he was able to cover the immense extent of ground which Scepticism thenceforward disputed with the dogmatic schools. Nor were his attacks directed against Stoicism only, but against all other positive systems past and present as well. What he says about the supposed foundation of knowledge is even now an unanswerable objection to the transcendental realism of Mr Herbert Spencer. States of consciousness speak for themselves alone, they do not include the consciousness of an external cause.234 But the grounds on which he rests his negation of all certainty are still superficial enough, being merely those sensible illusions which the modern science of observation has been able either to eliminate altogether or to restrict within narrow and definable limits. That phenomena, so far from being necessarily referred to a cause which is not phenomenal, cannot be thought of at all except in relation to one another, and that knowledge means nothing more than a consciousness of this relation, was hardly perceived before the time of Hume.
Turning from sense to reason, Carneades attacks the syllogistic process on grounds already specified in connexion with the earlier Sceptics; and also on the plea that to prove the possibility of syllogism is itself to syllogise, and thus involves either a petitio principii or a regress ad infinitum.235 Such a method is, of course, suicidal, for it disproves the possibility of the alleged disproof, a consideration which the Stoics did not fail to urge, and which the later Sceptics could only meet by extending the rule of suspense to their own arguments against argument.236 Nevertheless the sceptical analysis detected some difficulties in the ordinary theory of logic, which have been revived in modern times, and have not yet received any satisfactory solution. Sextus Empiricus, probably copying an earlier authority, it may be Carneades himself, observes that, as the major premise of every syllogism virtually contains the minor, it is either superfluous, or assumes the proposition to be proved. Thus we argue that Socrates is an animal because he is a man, and all men are animals. But if we do not know this latter proposition to be true in the case of Socrates, we cannot be sure that it is true in any case; while if we know it to be true in his case, we do not need to begin by stating it in general terms. And he also attempts to show the impossibility of a valid induction by the consideration, since so often urged, that to generalise from a limited number of instances to a whole class is unsafe, for some of the unknown instances may be contradictory, while the infinite, or at least indefinite multiplicity of individuals precludes the possibility of their exhaustive enumeration.237
When the Academicians pass from the form to the matter of dogmatic philosophy, their criticisms acquire greater interest and greater weight. On this ground, their assaults are principally directed against the theology of their Stoic and Epicurean rivals. It is here in particular that Carneades reveals himself to us as the Hume of antiquity. Never has the case for agnosticism been more powerfully made out than by him or by the disciples whom he inspired. To the argument for the existence of supernatural beings derived from universal consent, he replies, first, that the opinion of the vulgar is worthless, and secondly, that men’s beliefs about the gods are hopelessly at variance with one another, even the same divinity being made the subject of numberless discordant legends.238 He reduces the polytheistic deification of natural objects to an absurdity by forcing it back through a series of insensible gradations into absolute fetichism.239 The personification of mental qualities is similarly treated, until an hypothesis is provided for every passing mood.240 Then, turning to the more philosophical deism of the Stoics, he assails their theory of the divine benevolence with instance after instance of the apparent malevolence and iniquity to be found in Nature; vividly reminding one of the facts adduced by Mr. Herbert Spencer in confutation of the similar views held by modern English theologians.241 As against the whole theory of final causes, Carneades argues after a method which, though logically sound, could not then present itself with the authority which advancing science has more recently shown it to possess. ‘What you Stoics,’ he says, ‘explain as the result of conscious purpose, other philosophers, like Strato for instance, explain with equal plausibility as the result of natural causation. And such is our ignorance of the forces at work in Nature that even where no mechanical cause can be assigned, it would be presumptuous to maintain that none can exist.242 The reign of law does not necessarily prove the presence of intelligence; it is merely the evidence of a uniform movement quite consistent with all that we know about the working of unconscious forces.243 To contend, with Socrates, that the human mind must be derived from a Universal Mind pervading all Nature would logically involve the transfer of every human attribute to its original source.244 And to say that the Supreme Being, because it surpasses man, must possess an intelligence like his, is no more rational than to make the same assumption with regard to a great city because it is superior to an ant.’245
The materialism of his dogmatic contemporaries placed them at a terrible disadvantage when the sceptical successor of Plato went on to show that eternal duration is incompatible with whatever we know about the constitution of corporeal substance; and this part of his argument applied as much to the Epicurean as to the Stoic religion.246 But even a spiritualistic monotheism is not safe from his dissolving criticism. According to Carneades, a god without senses has no experience of whatever pleasurable or painful feelings accompany sensation, and is therefore, to that extent, more ignorant than a man; while to suppose that he experiences painful sensations is the same as making him obnoxious to the diminished vitality and eventual death with which they are naturally associated. And, generally speaking, all sensation involves a modification of the sentient subject by an external object, a condition necessarily implying the destructibility of the former by the latter.247 So also, moral goodness is an essentially relative quality, inconceivable without the possibility of succumbing to temptation, which we cannot attribute to a perfect Being.248 In a word, whatever belongs to conscious life being relative and conditioned, personality is excluded from the absolute by its very definition.
As to the proofs of divine agency derived from divination, they are both irrational and weak. If all things are predetermined by God’s providence, knowledge of the future is useless, and, therefore, cannot have been given to us. Moreover, no confidence can be placed in the alleged fulfilments of prophecy; probably most of them are fictitious and the remainder accidental. For the rest, good luck is distributed without regard to merit; and the general corruption of mankind shows that, from the Stoic point of view, human nature is a complete failure.249
Well may M. Havet say of the Academicians: ‘ce sont eux et non les partisans d’Epicure qui sont les libres penseurs de l’antiquité ou qui l’auraient voulu être; mais ils ne le pouvaient pas.’250 They could not, for their principles were as inconsistent with an absolute negation as with an absolute affirmation; while in practice their rule was, as we have said, conformity to the custom of the country; the consequence of which was that Sceptics and Epicureans were equally assiduous in their attendance at public worship. It is, therefore, with perfect dramatic appropriateness that Cicero puts the arguments of Carneades into the mouth of Cotta, the Pontifex Maximus; and, although himself an augur, takes the negative side in a discussion on divination with his brother Quintus. And our other great authority on the sceptical side, Sextus Empiricus, is not less emphatic than Cotta in protesting his devotion to the traditional religion of the land.251
We have seen with what freedom Carneades discussed the foundations of morality. It is now evident that in so doing he did not exceed the legitimate functions of criticism. No one at the present day looks on Prof. Bain and Mr. Henry Sidgwick as dangerous teachers because they have made it clear that to pursue the greatest happiness of the greatest number is not always the way to secure a maximum of happiness for oneself. The really dangerous method, as we now see, is to foster illusions in early life which subsequent experience must dispel.
With the introduction of practical questions, we pass to the great positive achievement of Carneades, his theory of probable evidence. Intended as an account of the process by which belief is adjusted to safe action rather than of the process by which it is brought into agreement with reality, his logic is a systematisation of the principles by which prudent men are unconsciously guided in common life. Carneades distinguishes three degrees of probability. The lowest is attached to simple perception. This arises when we receive the impression of an object without taking the attendant circumstances into account. The next step is reached when our first impression is confirmed by the similar impressions received from its attendant circumstances; and when each of these, again, bears the test of a similar examination our assurance is complete. The first belief is simply probable; the second is probable and uncontradicted; the third probable, uncontradicted, and methodically established. The example given by Sextus is that of a person who on seeing a coil of rope in a dark passage thinks that it may be a snake, and jumps over it, but on turning round and observing that it remains motionless feels inclined to form a different opinion. Remembering, however, that snakes are sometimes congealed by cold in winter, he touches the coil with his stick, and finally satisfies himself by means of this test that the image present to his mind does not really represent a snake. The circumstances to be examined before arriving at a definite judgment include such considerations as whether our senses are in a healthy condition, whether we are wide awake, whether the air is clear, whether the object is steady, and whether we have taken time enough to be sure that the conditions here specified are fulfilled. Each degree of probability is, again, divisible into several gradations according to the strength of the impressions received and the greater or less consilience of all the circumstances involved.252
The Academic theory of probability bears some resemblance to the Canonic of Epicurus, and may have been partially suggested by it. Both are distinguished from the Aristotelian and Stoic logic by the care with which they provide for the absence of contradictory evidence. In this point, however, the superiority of Carneades to Epicurus is very marked. It is not enough for him that a present impression should suggest a belief not inconsistent with past experience; in the true inductive spirit, he expressly searches for negative instances, and recommends the employment of experiment for this purpose. Still more philosophical is the careful and repeated analysis of attendant circumstances, a precaution not paralleled by anything in the slovenly method of his predecessor. Here the great value of scepticism as an element in mental training becomes at once apparent. The extreme fallibility of the intellectus sibi permissus had to be established before precautions could be adopted for its restraint. But the evidence accepted in proof of this fallibility has been very different at different times, and has itself given rise to more than one fallacious interpretation. With us it is, for the most part, furnished by experience. The circumstance that many demonstrable errors were formerly received as truths is quite sufficient to put us on our guard against untested opinions. With Bacon, it was not the erroneousness of previous systems, but their barrenness and immobility, which led him to question the soundness of their logic; and his doubts were confirmed by an analysis of the disturbing influences under which men’s judgments are formed. The ancient Sceptics were governed entirely by à priori considerations. Finding themselves confronted by an immense mass of contradictory opinions, they argued that some of these must be false as all could not possibly be true. And an analysis of the human faculties led them, equally on à priori grounds, to the conclusion that these irreconcilable divergences were but the result and the reproduction of an interminable conflict carried on within the mind itself. They could not foresee how much time would do towards reducing the disagreement of educated opinion within a narrower compass. They did not know what the experience of experience itself would teach. And their criticisms on the logic and metaphysics of their opponents were rendered inconclusive, as against all certainty, by the extent to which they shared that logic and metaphysics themselves. Carneades, at least, seems to assume throughout that all existence is material, that there is a sharp distinction between subject and object in knowledge, and that there is an equally sharp distinction between sensation and reasoning in the processes by which knowledge is obtained. In like manner, his ethical scepticism all turns on the axiom, also shared by him with the Stoics, that for a man to be actuated by any motive but his own interest is mere folly.