PROLEGOMENA TOANYFUTUREMETAPHYSICS 801
to things in themselves, since this never can be done by the dissection of our concepts (in
analytical propositions)? For I do not want to know what is contained in my concept of a
thing (for that belongs to its logical essence), but what in the actuality of the thing is
superadded to my concept and by which the thing itself is determined in its existence
apart from the concept. My understanding and the conditions on which alone it can
connect the determination of things in their existence do not prescribe any rule to things
[in] themselves; these do not conform to my understanding, but it would have to conform
itself to them; they would therefore have to be first given me in order to gather these
determinations from them, wherefore they would not be known a priori.
But knowledge of the nature of things in themselves a posterioriwould be
equally impossible. For, if experience is to teach us laws to which the existence of
things is subject, these laws, if they have reference to things in themselves, would have
to hold them of necessity even outside our experience. But experience teaches us what
exists and how it exists, but never that it must necessarily exist so and not otherwise.
Experience therefore can never teach us the nature of things in themselves.
§ 15. We nevertheless actually possess a pure science of nature in which are
propounded,a prioriand with all the necessity requisite to apodictical propositions,
laws to which nature is subject. I need only call to witness that propaedeutic of natural
science which, under the title of the universal science of nature, precedes all physics
(which is founded upon empirical principles). In it we have mathematics applied to
appearances, and also merely discursive principles (or those derived from concepts),
which constitute the philosophical part of the pure knowledge of nature. But there are
several things in it which are not quite pure and independent of empirical sources, such
as the concept of motion,that of impenetrability(upon which the empirical concept of
matter rests), that of inertia,and many others, which prevent its being called a perfectly
pure science of nature. Besides, it only refers to objects of the outer sense, and therefore
does not give an example of a universal science of nature, in the strict sense, for such a
science must bring nature in general, whether it regards the object of the outer or that of
the inner sense (the object of physics as well as psychology), under universal laws. But
among the principles of this universal physics there are a few which actually have the
required universality; for instance, the propositions that “substance is permanent,” that
“every event is determined by a cause according to constant laws,” etc. These are actu-
ally universal laws of nature, which hold completely a priori.There is then in fact a
pure science of nature, and the question arises,How is it possible?
§ 16. The word natureassumes yet another meaning which defines the object,
whereas in the former sense it only denotes the conformity to law of the determinations of
the existence of things generally. If we consider it materialiter,“nature is the complex of
all the objects of experience.” And with this only are we now concerned, for anyhow
things which can never be objects of experience, if they had to be known as to their nature,
would oblige us to have recourse to concepts whose meaning could never be given in con-
creto(by any example of possible experience). Consequently we would have to form for
ourselves a list of concepts of their nature, the reality whereof could never be determined.
That is, we could never learn whether they actually referred to objects or were mere
creations of thought. The knowledge of what cannot be an object of experience would be
hyperphysical, and with things hyperphysical we are here not concerned, but only with the
knowledge of nature, the actuality of which can be confirmed by experience, though this
knowledge is possible a prioriand precedes all experience.
§ 17. The formal aspect of nature in this narrower sense is therefore the conformity
to law of all the objects of experience and, so far as it is known a priori,their necessary
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