Understanding vs Reason

In the third part Kant talks about the difference between understanding and reason. He says that this is a big problem that arises in philosophical thinking. Hume says that any concept that can be associated with experience belongs under the category of understanding. While when we use reason we are striving not to use experience, experience only causes problems in reasoning. Kant comes up with three different ideas of reason, psychological ideas, cosmological ideas, and the theological ideas.

Looking at psychological ideas we are trying to find some sort of thing or subject that is underlying all the predicates we apply to the subject. For example when looking at a fish we may say the thing with scales that thing that lives in water and so on, but what is the thing. Kant says that this is worthless and just wasting time. These things help us understand things by allowing us to apply concepts to empirical intiotions and concepts take the style of predicates. The cosmological idea is simply an idea thats object can not be used in any experience. Basically that we use reason to prove four thesis and antithesis about the world and how it is. Lastly the third type is theological which unlike the other two do not start from experience. We start rather with the idea of pure completness of a thing (a perfect being) to determine the possibility and thus the actuality of all other things.