Epistemology. Broadly, the discipline which discusses knowledge and seeks to express just how it is that we come to have it. I think we live in an age that is obsessed with epistemology. And I think that this raises quite a few problems.
Let me explain to you how I see the history of this issue. When I was studying philosophy at A level, we used to talk a lot about rationalists and empiricists. Your average rationalist privileges thought over experience, whilst your common or garden empiricist thinks that experience is what is most important. This is, of course, an over-simplification, but it helps us to see two big epistemological traditions in western philosophy. At the head of each stands a greek.
Plato is, if you like, King of the Rationalists. He thinks that what you see around you is all just shadow. What can be thought is much more important than what can be sensed. Plato loves maths, and also a good bit of mysticism, because these things are in the mind. He thinks general and universal things are much more exciting than particular or limited things. He loves to make systems of thought that are internally coherent, and barely cares whether these systems match the shadowy empirical world around him.
Aristotle, on the other hand, is Captain Empiricist. He loves to look around him at the world. He considers the main source of truth to be the senses, and thoughts are to be directed by experience rather than vice versa. He takes a keen interest in particular things - he enjoys cataloguing animals, for example - and is much less interested in mysticism. He likes logic - a lot- but mainly because it helps with the exploration and understanding of the world around him.
The philosophical descendants of Plato and Aristotle bickered for centuries.
The genius of the Enlightenment is the construction of a worldview which binds rationalism and empiricism tightly together. Science - as opposed to the random observation of facts in nature - is a perfect blend of rationalism and empiricism. A system is thought which explains prior (perhaps haphazard) observations, and then observations are made (systematically) to test the system. Plato and Aristotle are friends. Good friends. Their love-child (eww) is Kant, because Kant extends (or attempts to extend) the scientific method to metaphysics, and with it ethics and religion. He is quite explicit about this endeavour, and he really thinks that he has done it in his critical philosophy. No need to go into detail on that here.
So from Kant onward, ratio-empricism rules the roost in epistemological discussion.
Tomorrow: why ratio-empiricism is very, very bad...