Kant, Prolegomena to any Future Metaphysic

Some synthetic propositions can be known a priori

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Unformatted text preview: ’ and ask that my idealism be called ‘critical’. But if it really is an objectionable idealism to convert actual things (not appearances) into mere representations, by what name shall we call the idealism that goes the opposite way and changes mere representations into things? It may, I think, be called ‘dreaming idealism’, in contrast to the former, which may be called ‘visionary’. Both are refuted by my transcendental idealism - or, better, critical idealism. 27 SECOND PART OF THE MAIN TRANSCENDENTAL PROBLEM: How is pure natural science possible? Section 14 ·The word ‘nature’ has two senses. I shall employ the word in what I shall later call its ‘formal’ sense in this section and the next, and then in section 16 I shall start to use ‘nature’ in what I call its ‘material’ sense. Both will be in play in section 36·. Nature is the existence of things insofar as it is governed by universal ·causal· laws. If this meant the existence of things in themselves, we could not know nature either Ÿa priori o r Ÿa posteriori. Ÿ·One way of knowing things a priori is knowing them through the analysis of concepts·. We could not know nature as it is in itself in that way, because knowledge of what things are like in themselves can never come from analytically dissecting our concepts: we are not asking what is contained in our concept of the thing, but rather about what is added t o this concept in the reality of the thing itself. Ÿ·Some synthetic propositions can be known a priori because their truth is assured by the nature of our understanding, somewhat in the way that mathematical truths can be known a priori because our sensibility assures their truth. But this is also not applicable to the supposed ‘knowledge of nature as it is in itself’, which we are discussing·. My understanding ·has an effect on how things appear t o me, but it· cannot dictate what things are like i n themselves. They don’t have to conform to it; so if I am to know about things in themselves my understanding must conform to them, ·not vice versa·. That means that I couldn’t know about them until they had somehow been presented to me; which is to say that I couldn’t know them a priori. ŸNor could I have a posteriori knowledge - ·that is, knowledge through experience· of the nature of things in themselves. If I am to bring things under ·causal· laws, these laws must apply to them necessarily, and experience could never show me how things must be - only that they exist and what they are like. So it can never teach me the nature of things in themselves. Section 15 Yet we do have pure natural science, which discovers a priori certain laws that govern all of nature, and discovers them to be necessary. One part of it is what we call ‘general natural science’, which is a preliminary to empirical physics. In this we find Ÿmathematics applied to appearances ·on the basis of Ÿintuition·, and also Ÿconceptual principles that make up the Ÿphilosophical part of pure knowledge of nature. ·A couple of qualifications should be mentioned·. ŸIt is not strictly pure, because there are things in it that are based on experience, such as the concepts of motion, of impenetrability, of inertia. ŸNor is it ‘general’ in the strictest sense, because it concerns only the objects of the outer senses, whereas a truly general natural science would apply laws to the whole of nature - not only outer objects (physics) but also inner ones (psychology). Still, some principles of this general physics are strictly universal, for instance the propositions ‘Substance is permanent’ and ‘Everything that happens is determined by a cause according to constant laws’. These really are universal laws of nature that we can know a priori. So pure natural science does exist, and we have to ask: How is it possible? 28 Section 16 I now want to use the word ‘nature’ in a broader sense, its material’ sense, in which it refers to ·every aspect of· Ÿthe totality of all objects of ·possible· experience, that is, the whole perceivable world. Until this point I have been using ‘nature’ in its narrower sense, making it refer only to Ÿthe way all things fall under the system of laws. The perceivable world is all we have to concern ourselves with. If we tried to learn about things that couldn’t be objects of experience, we would have to think about them through concepts that could not be illustrated or cashed out in terms of any possible experience. Such concepts would be empty; we ·could play around with them in our minds, but· we could never know whether they applied to anything rather than being mere fictions that we had contrived. Knowledge of something that couldn’t be an object of experience would be supernatural ·in the quite literal sense of being above nature·, and the supernatural is no part of our present concern. The knowledge that we care about is the sort which, although it Ÿprecedes experience ·rather than Ÿarising out of it·, can Ÿbe confirmed by experience. Section 17 It has just been shown that the law...
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