HCJ: Kant

Immanuel Kant was a German philosopher that sought to reject the epistemology of Hume. He rejected Hume's idea that people were irrational and thought it was essential that humans should be rational, so that they could be moral and free.

Kant believe he had a stronger form of Hume's a priori knowledge, named synthetic a priori; knowledge that can be gained independently of experience. For example, if there was 1,000 living people in a football stadium and this is fact, you could also derive from that knowledge the minimum capacity of the stadium must be at least 1,000 people, you would also know the stadium could support human life and that time elapsing.

Through this, Kant has established the existence of both space and time. An object cannot possibly exist outside of time and space, they are the pre-conditions of all experience.

Kant supposedly saves science and metaphysics from scepticism, such as Hume's, in observing that every change has a cause and effect to nature. 

He rejects previous ideas that things exist if they are perceived, claiming they have to exist in order to perceive them; existence is a predicate of perception. Although Kant suggests reality is shaped by our perception, his theory is not solipsist as he believes the universe exists independently of the mind.

Kant believes we perceive the world by processing raw data into 12 innate categories; unity, plurality (or not), totality (or not), reality, negation, extension (substance), cause and effect, community (likeness to other objects), possibility (or impossibility), existence (or non-existence) and necessity (or contingency).

Anything in the world that is observed fits into at least one of the above categories. Kant argues that our perceptions only exist in our minds as phenomena.

Phenomena; real objects in the mind as we perceive them.

Noumena; the object itself, rather than as it is perceived.

Any object has a dual nature; the way it is naturally and the way it is when we perceive it. We can never know the noumena as once an object it is perceived by us, it is the phenomena.

Kant's moral philosophy was called the Categorical Imperative. It was a set of maxims that should be lived by, regardless of the situation. Any action could only be justifiable moral if it could be universalised without contradiction. For example, stealing a loaf of bread to feed your starving family may seem justifiable, but stealing a car is not. However, as stealing is not acceptable in every situation, you have a contradiction, so in Kant's view, it would never be acceptable to steal.