Then again, Parmenides — and those who affirm that Ens Totum was essentially Unum, denying all plurality — had difficulties on their side to surmount. Ens could not be identical with Unum, nor was the name Ens, identical with the thing named Ens. Moreover, though Ens Unum was Totum, yet Totum was not identical with Ens or with Unum. Totum necessarily implied partes: but the Unum per se was indivisible or implied absence of parts. Though it was true therefore that Ens was both Unum and Totum, these two were both of them essentially different from Ens, and belonged to it only by way of adjunct accident. Parmenides was therefore wrong in saying that Unum alone existed.

Plato’s refutation throws light upon the doctrine of Antisthenes.

The reasoning here given from Plato throws some light upon the doctrine just now cited from Antisthenes. You cannot say (argues Plato against the advocates of duality) that two elements (Hot and Cold) are both of them Entia or Existent, because by so doing you call them one. You cannot say (argues Antisthenes) that Sokrates is good, brave, old, &c., because by such speech you call one thing three. Again, in controverting the doctrine of Parmenides, Plato urges, That Ens cannot be Unum, because it is Totum (Unum having no parts, while Totum has parts): but it may carry with it the accident Unum, or may have Unum applied to it as a predicate by accident. Here again, we have difficulties similar to those which perplexed Antisthenes. For the same reason that Plato will not admit, That Ens is Unum — Antisthenes will not admit, That Man is good. It appeared to him to imply essential identity between the predicate and the subject.

All these difficulties and others to which we shall come presently, noway peculiar to Antisthenes — attest the incomplete formal logic of the time: the want of a good theory respecting predication and the function of the copula.

Plato’s argument against the Materialists.

Pursuing the purpose of establishing his conclusion (viz. That Ens involved as many perplexities as Non-Ens), Plato comes to the two opposite sects:— 1. Those (the Materialists) who recognised bodies and nothing else, as the real Entia or Existences. 2. Those (the Friends of Forms, the Idealists) who maintained that incorporeal and intelligible Forms or Species were the only real existences; and that bodies had no existence, but were in perpetual generation and destruction.102

Respecting the first, Plato says that they must after all be ashamed not to admit, that justice, intelligence, &c., are something real, which may be present or absent in different individual men, and therefore must exist apart from all individuals. Yet justice and intelligence are not bodies. Existence therefore is something common to body and not-body. The characteristic mark of existence is, power or potentiality. Whatever has power to act upon any thing else, or to be acted on by any thing else, is a real Ens or existent something.103

Reply open to the Materialists.

Unfortunately we never know any thing about the opponents of Plato, nor how they would have answered his objection — except so much as he chooses to tell us. But it appears to me that the opponents whom he is here confuting would have accepted his definition, and employed it for the support of their own opinion. “We recognise (they would say) just men, or hard bodies, as existent, because they conform to your definition: they have power to act and be acted upon. But justice, apart from just men — hardness, apart from hard bodies — has no such power: they neither act upon any thing, nor are acted on by any thing: therefore we do not recognise them as existent.” According to their view, objects of perception acted on the mind, and therefore were to be recognised as existent: objects of mere conception did not act on the mind, and therefore had not the same claim to be ranked as existent: or at any rate they acted on the mind in a different way, which constitutes the difference between the real and unreal. Of this difference Plato’s definition takes no account.104

Plato’s argument against the Idealists or Friends of Forms. Their point of view against him.

Plato now presents this same definition to the opposite class of philosophers: to the Idealists, or partisans of the incorporeal — or of self-existent and separate Forms. These thinkers drew a marked distinction between the Existent and the Generated — between Ens and Fiens — τὸ ὂν and τὸ γιγνόμενον. Ens or the Existent was eternal and unchangeable: Fiens or the Generated was always in change or transit, coming or going. We hold communion (they said) with the generated or transitory, through our bodies and sensible perceptions: we hold communion with unchangeable Ens through our mind and by intellection. They did not admit the definition of existence just given by Plato. They contended that that definition applied only to Fiens or to the sensible world — not to Ens or the intelligible world.105 Fiens had power to act and be acted upon, and existed only under the condition of being so: that is, its existence was only temporary, conditional, relative: it had no permanent or absolute existence at all. Ens was the real existent, absolute and independent — neither acting upon any thing nor being acted upon. They considered that Plato’s definition was not a definition of Existence, or the Absolute: but rather of Non-Existence, or the Relative.

Plato argues — That to know, and be known, is action and passion, a mode of relativity.

But (asks Plato in reply) what do you mean by “the mind holding communion” with the intelligible world? You mean that the mind knows, comprehends, conceives, the intelligible world: or in other words, that the intelligible world (Ens) is known, is comprehended, is conceived, by the mind. To be known or conceived, is to be acted on by the mind.106 Ens, or the intelligible world, is thus acted upon by the mind, and has a power to be so acted upon: which power is, in Plato’s definition here given, the characteristic mark of existence. Plato thus makes good his definition as applying to Ens, the world of intelligible Forms — not less than to Fiens, the world of sensible phenomena.

The definition of existence, here given by Plato, and the way in which he employs it against the two different sects of philosophers — Materialists and Idealists — deserves some remark.

Plato’s reasoning — compared with the points of view of both.

In this portion of the present dialogue (Sophistês) the point which he makes is, to show to the Idealists, or Absolutists, that their Forms are not really absolute, or independent of the mind: that the existence of these forms is relative, just as much as that of the sensible world. The sensible world exists relatively to our senses, really or potentially exercised: the intelligible world exists relatively to our intelligence, really or potentially exercised. In both cases alike, we hold communion with the two worlds: the communion cannot be left out of sight, either in the one case or in the other. The communion is the entire and fundamental fact, of which the Subject conceiving and the Object conceived, form the two opposite but inseparable faces — the concave and convex, to employ a favourite illustration of Aristotle. Subject conceiving, in communion with Object conceived, are one and the same indivisible fact, looked at on different sides. This is, in substance, what Plato urges against those philosophers who asserted the absolute and independent existence of intelligible Forms. Such forms (he says) exist only in communion with, or relatively to, an intelligent mind: they are not absolute, not independent: they are Objects of intelligence to an intelligent Subject, but they are nothing without the Subject, just as the Subject is nothing without them or some other Object. Object of intelligence implies an intelligent Subject: Object of sense implies a sentient Subject. Thus Objects of intelligence, and Objects of sense, exist alike relatively to a Subject — not absolutely or independently.

The argument of Plato goes to an entire denial of the Absolute, and a full establishment of the Relative.

Coincidence of his argument with the doctrine of Protagoras in the Theætêtus.

The argument here urged by Plato coincides in its drift and result with the dictum of Protagoras — Man is the measure of all things. In my remarks on the Theætêtus,107 I endeavoured to make it appear that the Protagorean dictum was really a negation of the Absolute, of the Thing in itself, of the Object without a Subject:— and an affirmation of the Relative, of the Thing in communion with a percipient or concipient mind, of Object implicated with Subject — as two aspects or sides of one and the same conception or cognition. Though Plato in the Theætêtus argued at length against Protagoras, yet his reasoning here in the Sophistês establishes by implication the conclusion of Protagoras. Here Plato impugns the doctrine of those who (like Sokrates in his own Theætêtus) held that the sensible world alone was relative, but that the intelligible world or Forms were absolute. He shows that the latter were no less relative to a mind than the former; and that mind, either percipient or cogitant, could never be eliminated from “communion” with them.

The Idealists maintained that Ideas or Forms were entirely unchangeable and eternal. Plato here denies this, and maintains that ideas were partly changeable, partly unchangeable.

These same Idealist philosophers also maintained — That Forms, or the intelligible world, were eternally the same and unchangeable. Plato here affirms that this ideas or opinion is not true: he contends that the intelligible world includes both change and unchangeableness, motion and rest, difference and sameness, life, mind, intelligence, &c. He argues that the intelligible world, whether assumed as consisting of one Form or of many Forms, could not be regarded either as wholly changeable or wholly unchangeable: it must comprise both constituents alike. If all were changeable, or if all were unchangeable, there could be no Object of knowledge; and, by consequence, no knowledge.108 But the fact that there is knowledge (cognition, conception), is the fundamental fact from which we must reason; and any conclusion which contradicts this must be untrue. Therefore the intelligible world is not all homogeneous, but contains different and even opposite Forms — change and unchangeableness — motion and rest — different and same.109

Plato’s reasoning against the Materialists.

Let us now look at Plato’s argument, and his definition of existence, as they bear upon the doctrine of the opposing Materialist philosophers, whom he states to have held that bodies alone existed, and that the Incorporeal did not exist:— in other words that all real existence was concrete and particular: that the abstract (universals, forms, attributes) had no real existence, certainly no separate existence. As I before remarked, it is not quite clear what or how much these philosophers denied. But as far as we can gather from Plato’s language, what they denied was, the existence of attributes apart from a substance. They did not deny the existence of just and wise men, but the existence of justice and wisdom, apart from men real or supposable.

Difference between Concrete and Abstract, not then made conspicuous. Large meaning here given by Plato to Ens — comprehending not only objects of Perception, but objects of Conception besides.

Narrower meaning given by Materialists to Ens — they included only Objects of Perception. Their reasoning as opposed to Plato.

Now the friends of the Concrete, against whom Plato reasons, used the word existent in a narrower sense, as comprising only the concretes of the sensible world. They probably admitted the existence of the abstract, along with and particularised in the concrete: but they certainly denied the separate existence of the Abstract — i.e., of Forms, Attributes, or classes, apart from particulars. They would not deny that many things were conceivable, more or less dissimilar from the realities of the sensible world: but they did not admit that all those conceivable things ought to be termed existent or realities, and put upon the same footing as the sensible world. They used the word existent to distinguish between Men, Horses, Trees, on the one hand — and Cyclopes, Centaurs, Τραγέλαφοι, &c., on the other. A Centaur is just as intelligible and conceivable as either a man or a horse; and according to this definition of Plato, would be as much entitled to be called really existent. The attributes of man and horse are real, because the objects themselves are real and perceivable: the class man and the class horse is real, for the same reason: but the attributes of a Centaur, and the class Centaurs, are not real, because no individuals possessing the attributes, or belonging to the class, have ever been perceived, or authenticated by induction. Plato’s Materialist opponents would here have urged, that if he used the word existent or Ens in so wide a sense, comprehending all that is conceivable or nameable, fiction as well as reality — they would require some other words to distinguish fiction from reality — Centaur from Man: which is what most men mean when they speak of one thing as non-existent, another thing as existent. At any rate, here is an equivocal sense of the word Ens — a wider and a narrower sense — which, we shall find frequently perplexing us in the ancient metaphysics; and which, when sifted, will often prove, that what appears to be a difference of doctrine, is in reality little more than a difference of phraseology.110

Different definitions of Ens — by Plato — the Materialists, the Idealists.

This enquiry respecting Ens is left by Plato professedly unsettled; according to his very frequent practice. He pretends only to have brought it to this point: that Ens or the Existent is shown to present as many difficulties and perplexities as Non-Ens or the non-existent.111 I do not think that he has shown thus much; for, according to his definition, Non-Ens is an impossibility: the term is absolutely unmeaning: it is equivalent to the Unknowable or Inconceivable — as Parmenides affirmed it to be. But he has undoubtedly shown that Ens is in itself perplexing: which, instead of lightening the difficulties about Non-Ens, aggravates them: for all the difficulties about Ens must be solved, before you can pretend to understand Non-Ens. Plato has shown that Ens is used in three different meanings:—

1. According to the Materialists, it means only the concrete and particular, including all the attributes thereof, essential and accidental.

2. According to the Idealists or friends of Forms, it means only Universals, Forms, and Attributes.

3. According to Plato’s own definition here given, it means both the one and the other: whatever the mind can either perceive or conceive: whatever can act upon the mind in any way, or for any time however short. It is therefore wholly relative to the mind: yet not exclusively to the perceiving mind (as the Materialists said), nor exclusively to the conceiving mind (as the friends of Forms said): but to both alike.

Plato’s views about Non-Ens examined.

Here is much confusion, partly real but principally verbal, about Ens. Plato proceeds to affirm, that the difficulty about Non-Ens is no greater, and that it admits of being elucidated. The higher Genera or Forms (he says) are such that some of them will combine or enter into communion with each other, wholly or partially, others will not, but are reciprocally exclusive. Motion and Rest will not enter into communion, but mutually exclude each other: neither of them can be predicated of the other. But each or both of them will enter into communion with Existence, which latter may be predicated of both. Here are three Genera or Forms: motion, rest, and existence. Each of them is the same with itself, and different from the other two. Thus we have two new distinct Forms or Genera — Same and Different — which enter into communion with the preceding three, but are in themselves distinct from them.112 Accordingly you may say, motion partakes of (or enters into communion with) Diversum, because motion differs from rest: also you may say, motion partakes of Idem, as being identical with itself: but you cannot say, motion is different, motion is the same; because the subject and the predicate are essentially distinct and not identical.113

Some things are always named or spoken of per se, others with reference to something else. Thus, Diversum is always different from something else: it is relative, implying a correlate.114 In this, as well as in other points, Diversum (or Different) is a distinct Form, Genus, or Idea, which runs through all other things whatever. Each thing is different from every other thing: but it differs from them, not through any thing in its own nature, but because it partakes of the Form or Idea of Diversum or the Different.115 So, in like manner, the Form or Idea of Idem (or Same) runs through all other things: since each thing is both different from all others, and is also the same with itself.

His review of the select Five Forms.

Again, motion is different from Idem or the Same. It is therefore not the same. Yet still motion is the same; because every thing partakes of identity, or is the same with itself. Motion therefore both is the same and is not the same. We must not scruple to advance both these propositions. Each of them stands on its own separate ground.116 So also motion is different from Diversum or The Different; in other words, it is not different, yet still it is different. And, lastly, motion is different from Ens, in other words, it is not Ens, or is non-Ens: yet still it is Ens, because it partakes of existence. Hence motion is both Ens, and Non-Ens.

Here we arrive at Plato’s explanation of Non-Ens, τὸ μὴ ὂν: the main problem which he is now setting to himself. Non-Ens is equivalent to, different from Ens. It is the Form or Idea of Diversum, considered in reference to Ens. Every thing is Ens, or partakes of entity, or existence. Every thing also is different from Ens, or partakes of difference in relation to Ens: it is thus Non-Ens. Every thing therefore is at the same time both Ens, and Non-Ens. Nay, Ens itself, inasmuch as it is different from all other things, is Non-Ens in reference to them. It is Ens only as one, in reference to itself: but it is Non-Ens an infinite number of times, in reference to all other things.117

Plato’s doctrine — That Non-Ens is nothing more than different from Ens.

When we say Non-Ens, therefore (continues Plato), we do not mean any thing contrary to Ens, but merely something different from Ens. When we say Not-great, we nothing do not mean any thing contrary to Great, but only something different from great. The negative generally, when annexed to any name, does not designate any thing contrary to what is meant by that name, but something different from it. The general nature or Form of difference is disseminated into a multitude of different parts or varieties according to the number of different things with which it is brought into communion: Not-great, Not-just, &c., are specific varieties of this general nature, and are just as much realities as great, just. And thus Non-Ens is just as much a reality as Ens being not contrary, but only that variety of the general nature of difference which corresponds to Ens. Non-Ens, Not-great, Not-just, &c., are each of them permanent Forms, among the many other Forms or Entia, having each a true and distinct nature of its own.118

I say nothing about contrariety (concludes Plato), or about any thing contrary to Ens; nor will I determine whether Non-Ens in this sense be rationally possible or not. What I mean by Non-Ens is a particular case under the general doctrine of the communion or combination of Forms: the combination of Ens with Diversum, composing that which is different from Ens, and which is therefore Non-Ens. Thus Ens itself, being different from all other Forms, is Non-Ens in reference to them all, or an indefinite number of times119 (i.e. an indefinite number of negative predications may be made concerning it).

Non-Ens being thus shown to be one among the many other Forms, disseminated among all the others, and entering into communion with Ens among the rest — we have next to enquire whether it enters into communion with the Form of Opinion and Discourse. It is the communion of the two which constitutes false opinion and false proposition: if therefore such communion be possible, false opinion and false proposition are possible, which is the point that Plato is trying to prove.120

Communion of Non-Ens with proposition — possible and explicable.

Now it has been already stated (continues Plato) that some Forms or Genera admit of communion with each other, others do not. In like manner some words admit of communion with each other — not others. Those alone admit of communion, which, when put together, make up a proposition significant or giving information respecting Essence or Existence. The smallest proposition must have a noun and a verb put together: the noun indicating the agent, the verb indicating the act. Every proposition must be a proposition concerning something, or must have a logical subject: every proposition must also be of a certain quality. Let us take (he proceeds) two simple propositions: Theætêtus is sitting down — Theætêtus is flying.121 Of both these two, the subject is the same: but the first is true, the second is false. The first gives things existing as they are, respecting the subject: the second gives respecting the subject, things different from those existing, or in other words things non-existent, as if they did exist.122 A false proposition is that which gives things different as if they were the same, and things non-existent as if they were existent, respecting the subject.123