Immanuel Kant was a highly significant transitional figure between the 18th and 19th centuries. Up until this time the debate between the Continental rationalists and the British empiricists had continued to broil. However, the debate between the rationalists and empiricists prompted Immanuel Kant to highlight the differences between the kinds of statements, judgments, or propositions and to propose a solution to the epistemological conclusions of the rationalists and empiricists. For Kant the distinctions between analytic and synthetic and a priori and a posteriori judgments must be kept separate. Kant proposes four types of propositions:
1) Analytical: These are statements in which the predicate is part of the subject. An example of an analytical statement is, "A bachelor is an unmarried man." By definition a "bachelor" is an unmarried man.
2) Synthetic: These are statements, which are learned by experience. An example of a synthetic statement is, "Birds are yellow." By definition, a "bird" is not yellow but that some are yellow is learned from experience.
3) A posterior statements: Again, these are statements, which are learned by experience. A posteriori statements are also synthetic statements.
4) A priori statements: Again, these are statements, which one knows before experience and by definition. A priori statements are also analytic statements.
All a posteriori statements are synthetic judgments.
All synthetic statements are not a posteriori judgments.
In mathematical and geometrical judgments, the predicate is not contained in the subject. For example the concept of 12 is not contained either in 7, 5, + or =. Neither is the predicate contained in the combination of these elements.
Such propositions are universal and necessary and are therefore a priori even though they could not have been known from experience. They would therefore synthetic a priori judgments though this seems contradictory.
Kant used this reality as a basis for his conclusions of the work of the rationalists and empiricists regarding the nature of knowledge. According to Kant epistemology is both rationalistic and empiricistic. The mind takes ideas and interprets them in light of categories such as space, time, quantity, qualities, relationships, and modality. All of these categories are subject to and are built into the mind.
All rational beings think of the world in terms of space, time and categories such as cause and effect, substance, unity, plurality, necessity, possibility, and reality. We think of things in this manner not because that is actually the way the world is but because that is the way our minds order experience.
Sense data is interpreted by these innate categories in the mind. In other words, the mind takes the sensory data and interprets it through these innate categorical grids. In short, reason provides the structure or form of what we know and the senses provide the content of what we know. In another sense, Kant is saying that sensory experience constitutes the "software" of what we know and reason provides the "hardware" by which the "software" is interpreted and stored.
Knowledge is possible not because it is about the way things actually are, but because it is about how things appear to be.
