Judgments of perception and judgments of experience
Written by Jason Zarri
Article by Jason Zarri (1986 - 2014) Aspiring philosopher, writer, and co-founder of Scholardarity, a website for scholars and students in the Humanities - http://www.scholardarity.com/wp-content/ uploads/2012/09/Notes-on-Kant-draft-5-PDF.pdf.
1) We often observe that one appearance regularly succeeds another. For example, we may take notice of the fact that whenever a metal is heated, it expands. If we affirm that this is so, we have made a judgment of perception. But we don't stop there; usually, we go on to conclude that heating a metal causes it to expand. Now we have a judgment of experience, in which two or more appearances are linked through a pure concept of the understanding, in this case the concept of causation. The faculty of understanding is active. It is the source of pure concepts, which are used to organize our perceptions and bind them together into experience. And though the function of pure concepts is to turn perception into experience, they are not derived from them (Prolegomena, p. 60).
2) Returning to the above example, the judgment that whenever a metal is heated it expands is a judgment of perception, as it involves no pure concepts of the understanding. However, if I judge that heating a metal causes it to expand, I subsume the concepts of the metal's being heated and its expanding under the pure concept of cause and effect. In the judgment of perception we have subjective validity, for it asserts only a constant conjunction, which does not carry with it any hint of necessity or universality. But in the judgment of experience we have both, for it asserts a necessary relation between two concepts, and for that reason it must always hold, not only for oneself but for everyone. Thus judgments of experience are objectively valid (Prolegomena, pp. 45-47).
3) Kant agrees with David Hume that the concept of causation cannot be derived from experience. But unlike Hume, Kant does not think causation is merely a habitual association of concepts that we project onto external objects. Instead, he regards it as being a pure concept of the understanding, which the mind imposes on experience in order to make sense of it (Prolegomena, pp. 57-60). As such, it cannot have any application beyond the bounds of possible experience— or, at any rate, we cannot know whether it does.