WE proceed, in the ensuing Books, to the closer examination of a considerable number of those Fundamental Ideas on which the sciences, hitherto most successfully cultivated, are founded. In this task, our objects will be to explain and analyze such Ideas so as to bring into view the Definitions and Axioms, or other forms, in which we may clothe the conditions to which our speculative knowledge is subjected. I shall also try to prove, for some of these Ideas in particular, what has been already urged respecting them in general, that they are not derived from observation, but necessarily impose their conditions upon that knowledge of which observation supplies the materials. I shall further, in some cases, endeavour to trace the history of these Ideas as they have successively come into notice in the progress of science; the gradual development by which they have arrived at their due purity and clearness; and, as a necessary part of such a history, I shall give a view of some of the principal controversies which have taken place with regard to each portion of knowledge.
An exposition and discussion of the Fundamental Ideas of each Science may, with great propriety, be termed the Philosophy of such Science. These ideas contain in themselves the elements of those truths which the science discovers and enunciates; and in the progress of the sciences, both in the world at large and in the mind of each individual student, the most important steps consist in apprehending these ideas clearly, and in bringing them into accordance with the observed facts. I shall, therefore, in a series of Books, 82 treat of the Philosophy of the Pure Sciences, the Philosophy of the Mechanical Sciences, the Philosophy of Chemistry, and the like, and shall analyze and examine the ideas which these sciences respectively involve.
In this undertaking, inevitably somewhat long, and involving many deep and subtle discussions, I shall take, as a chart of the country before me, by which my course is to be guided, the scheme of the sciences which I was led to form by travelling over the history of each in order8. Each of the sciences of which I then narrated the progress, depends upon several of the Fundamental Ideas of which I have to speak: some of these Ideas are peculiar to one field of speculation, others are common to more. A previous enumeration of Ideas thus collected may serve both to show the course and limits of this part of our plan, and the variety of interest which it offers.
I shall, then, successively, have to speak Of the Ideas
which are the foundation of Geometry and Arithmetic, (and
which also regulate all sciences depending upon these, as
Astronomy and Mechanics;) namely, the Ideas of Space,
Time, and Number (Book ii.):
Of the Ideas on which the Mechanical Sciences (as Mechanics,
Hydrostatics, Physical Astronomy) more peculiarly rest; the
ideas of Force and Matter, or rather the idea
of Cause, which is the basis of these (Book iii.):
Of the Ideas which the Secondary Mechanical Sciences
(Acoustics, Optics, and Thermotics) involve; namely, the
Ideas of the Externality of objects, and of the
Media by which we perceive their qualities (Book iv.):
Of the Ideas which are the basis of Mechanico-chemical and
Chemical Science; Polarity, Chemical Affinity,
and Substance; and the Idea of Symmetry, a
necessary part of the Philosophy of Crystallography (Books
v. vi.):
Of the Ideas on which the Classificatory Sciences proceed
(Mineralogy, Botany, and Zoology); namely, 83 the Ideas of
Resemblance, and of its gradations, and of Natural
Affinity (Books vii. viii.):
Finally, of those Ideas on which the Physiological Sciences
are founded; the Ideas of separate Vital Powers, such as
Assimilation and Irritability; and the Idea of
Final Cause (Book ix.):
We have, besides these, the Palætiological Sciences, which
proceed mainly on the conception of Historical
Causation (Book x.):
It is plain that when we have proceeded so far as this, we have advanced to the verge of those speculations which have to do with mind as well as body. The extension of our philosophy to such a field, if it can be justly so extended, will be one of the most important results of our researches; but on that very account we must fully study the lessons which we learn in those fields of speculation where our doctrines are most secure, before we venture into a region where our principles will appear to be more precarious, and where they are inevitably less precise.
We now proceed to the examination of the above Ideas, and to such essays towards the philosophy of each Science as this course of investigation may suggest.