Enter the "savior of Western thought," Immanuel Kant (1724-1804). This quiet, unassuming professor in Konigsberg, Germany would have been nominated by none of his childhood friends to be known for anything. They would each have been wrong.

To simplify the notoriously complex Kant: we must rescue philosophy from the twin dead ends of pure rationalism and pure empiricism. How? The senses provide the "data" which the mind "interprets." The result is "knowledge."

Of course, we say. Everyone thinks that's true. Precisely the point.

Let's start with Kant's epistemology (as described in his Critique of Pure Reason, one of the most influential philosophical treatises of all time). Kant believed that your mind brings rational structures to reality. Rather than being impressed by reality through sense impressions only (as the empiricists said), your mind interprets these sense impressions. It uses innate (with Descartes) "categories" (not ideas, vs. Descartes). According to Kant, "although all our knowledge begins with experience it does not follow that it arises out of experience."

What are these categories, you ask? Kant provides the answer:

Quantity

(amount):
1. Unity

2. Plurality

3. Totality

Quality

(kind of material)
4. Reality

5. Negation

6. Limitation

Relation

(of substance to other substance)
7. Inherence and subsistence

8. Causality and dependence

9. Community

Modality

(of patterns within substances)
10. Possibility / impossibility

11. Existence / non-existence

12. Necessity / contingency

Let's (over)simplify things. Kant believed that he identified the key questions your mind inherently asks of every sense experience given to it: how much? what kind? how does it relate to other things? what patterns can we identify and predict? We cannot help asking these questions--this is the basic way our minds innately work.

To use an analogy totally foreign to Kant's world, think of your mind as the software resident in your computer. Your senses are the keyboard, being typed on by the external world. Your software interprets the keystrokes, resulting in "knowledge" which is imprinted on the disk drive and printed on paper.

Isn't this how everyone thinks that thinking works? Not before Kant.