This question, which is the highest point the transcendental philosophy can ever touch, and to which it must also, as its boundary and completion, be directed, properly comprises two questions.
Firstly: How is Nature, in its material signification, namely, as intuition, as the sum-total of phenomena—how is space, time, and that which fills them both, namely, the object of feeling in general—possible? The answer is, by means of the construction of our sensibility, in accordance with which, it is affected in a special manner by objects, in themselves unknown and entirely distinct from these appearances. This answer has been given in the book itself in the Transcendental Æsthetic, but in these Prolegomenain the solution of the first general question.
Secondly: How is Nature in its formalsignification—as the sum-total of the rules to which all phenomenamust be subordinated, if they are to be thought of as connected in an experience—possible? The answer can only be: It is only possible by means of the construction of our understanding, in accordance with which all the above presentations of sensibility are necessarily referred to a consciousness, and whereby the special manner of our thought (namely, by rules), and by means of these, experience (which is to be wholly distinguished from a knowledge of things in them- selves) is possible.…
But how this special property of our sensibility itself, or of our understanding together with the necessary appercep- tion lying at its basis, and at that of all thought, is possible, will not admit of any further solution or answer, because we invariably require it for all answers and for all thought of objects.
There are many laws of Nature that we can only know by means of experience, but regularity in the connection of phenomena, i.e., Nature in general, we can never learn through experience, because experience itself requires such laws, and these lie at the foundation of its possibility apriori. The possibility of experience in general is at once the universal law of Nature, and the axioms of the one are at the same time the laws of the other. For we know nothing of Nature otherwise than as the sum-total of phenomena, namely, of presentations in us, and hence can derive the law of their connection in no other way than from the principles of the same connection in ourselves; in other words, from the conditions of necessary union in a consciousness, which constitutes the possibility of experience.
Even the main proposition, worked out through the whole of this section, that universal natural laws are to be known apriori, of itself leads to the further proposition, that the highest legislation of Nature must lie in ourselves, namely, in our understanding, and that we must seek its universal laws, not in Nature, by means of experience; but conversely, must seek Nature, as to its universal regularity, solely in the conditions of the possibility of experience lying in our sensibility and understanding. For how would it otherwise be possible to know these laws aprioriif they be not rules of analytic knowledge, but actually synthetic extensions of the same? Such a necessary agreement of the principles of possible experience with the laws of the possibility of Nature can only occur from one of two causes; either the laws are borrowed from Nature by means of experience, or conversely, Nature is derived from the laws of the possibility of experience generally, and is entirely the same thing as the purely formal regularity of the latter. The first supposition contradicts itself, for the universal laws of Nature can and must be known apriori(i.e., independently of all experience), and be posited as the basis of the empirical use of the understanding; so that only the second [hypothesis] remains to us.
But we must distinguish the empirical laws of Nature, which always presuppose particular perceptions, from the pure or universal natural laws, which without any particular perceptions at their foundation, merely contain the conditions of their necessary union in an experience; and in respect of the last, Nature and possible experience are the same thing. Hence, as in this, the legitimacy rests on the necessary connection of phenomena in an experience, in other words, on the original laws of the understanding (without which we could cognise no object of the sensuous world whatever), it sounds at first singular, but is none the less certain, when I say in respect of the latter: The understanding draws its laws (apriori) not from Nature, but prescribes them to it. …
How is Natural Science possible?
Step One: Clarifying the problem
Natural science, despite appearances, includes a ‘pure’ (i.e., non-empirical) element. Every science makes two assumptions. What are they?
These assumptions are pre-conditions for even engaging in science in the first place.
Two main competitors: rationalism and (Lockean) empiricism. Neither works. So we need to start over and find a third way. Turn now to JOEs. What makes them possible?
But these just are the universal laws of nature (602). That is, the principles upon which all sciences depend also lie at the bottom of all _________, and make it possible.
So we’ve really got just one problem here: how can we justify claims that involve the pure concepts of the understanding, claims like cause, effect, substance, etc.?
Step Two: What did Hume teach us?
- These claims cannot be empirical. Why?
But nor can they be analytic. Why?
These are the prongs of Hume’s fork; for him, every proposition is either a matter of fact or a relation of ideas. Hume concludes that these principles have only __________ necessity; they are the ‘bastard offspring’ of __________ impregnated by _________.
Step Three: Putting it all together:
Hume is right to claim that experience can’t justify __________. But he’s wrong to think that this means that ____________________. Instead, the concept of cause and effect is a pure ____________________. That is, it is not something we read off from experience, but something we use to construct experience in the first place. There’s no room for skepticism about causation, since to have any experiences at all, I must be uniting __________ in judgments according to the concept of a cause. Like geometry, pure natural science depends on _____________________________.
Step Four: What are the consequences?
But just as with geometry, this means that the categories can be applied ____________________. Is Kant saying that things as they are in themselves must be connected by cause and effect, or that they are things at all, in the way a tree is a thing? __________, because ___________________.
Another way to see the same point: remember, all judgments require ____________________. Applied to things in themselves, the categories have __________. (See Section Thirty: The Second Part, Continued and
Section Thirty-four: The Second
Part, Continued). When we try to apply the categories to things in themselves, we leave out _________, and so generate only empty logical forms, structure without stuffing.