Were our intuition of such a nature as to present thingsastheyareinthemselves, no intuition aprioriwould take place at all, but it would always be empirical. For what is contained in the object in itself, I can only know when it is given and present to me. It is surely then inconceivable how the intuition of a present thing should enable me to know it as it is in itself, seeing that its properties cannot pass over into my presentative faculty. But granting the possibility of this, the said intuition would not take place apriori, that is, before the object was presented to me, for without it no ground of connection between my presentation and the object could be imagined; in which case it must rest on inspiration (Einge- bung). Hence there is only one way possible, by which my intuition can precede the reality of the object and take place as knowledge apriori, and that is, if it contain nothing else but that form of sensibility which precedes in my subject all real impressions, by which I am affected by objects. For, that objects of sense can only be intuited in accordance with this form of sensibility, is a fact I can know apriori. From this it follows, that propositions merely concerning the form of sensible intuition, will be valid and possible for all objects of sense; and conversely, that intuitions possible apriori, can never concern other things than objects of our sense.
- What would go wrong if the objects of synthetic a priori knowledge (propositions like ‘the shortest distance between two points is a straight line’) were supposed to tell us about things as they are in themselves?
- What then do such propositions tell us about?