Metaphysics
The field of philosophy that investigates the constitution, nature, and structure of reality. Metaphysics goes beyond physics to examine the reality behind the phenomenal world. It asks questions that cannot be verified in experience: "Does God exist?" "Is the soul immortal?" "What are the ultimate constituents of matter?" "How are mind and matter connected?" and so on. In the
Analytic
A statement whose predicate concept is contained in its subject concept. An example is "all bachelors are unmarried." The concept of being unmarried is part of the concept of "bachelor," so the predicate does not say anything new. Instead, it offers an analysis of a part of the concept of the subject.
Synthetic
A statement whose predicate concept is different from its subject concept. Such a statement joins two different concepts together, and in doing so, produces new and interesting judgments. The
a priori
Knowledge that can be gained prior to any experience. Mathematics is a form of
a posteriori
In contrast with
Intuition
A translation of the German word
Concept of the Understanding
These concepts, listed in Kant's table of categories, give a law-like structure to experience. While the empirical intuitions of our faculty of sensibility give us only subjective knowledge of experience, the faculty of understanding makes our empirical intuitions objective by applying to them universal concepts such as cause and substance. On their own, these concepts in their pure form serve as the basis for the general laws of pure natural science, such as "every effect has a cause."
Sensibility
The faculty that gives structure to the report of our senses. Our senses perceive things in themselves, and our faculty of sensibility applies our pure intuitions of space and time to give form to these sensations. Sensations combined with pure intuition makes empirical intuitions. The faculty of sensibility ensures that whatever we perceive we perceive in space and time.
Understanding
The faculty that gives an objective, law-like structure to our experience. Our faculty of sensibility gives us empirical intuitions, and our faculty of understanding applies to these intuitions the pure concepts of the understanding to give them objectivity. Empirical intuitions combined with pure concepts of the understanding make appearances. The faculty of understanding ensures that whatever we perceive, we perceive as following the laws of cause and effect and so on.
Reason
The faculty that deals exclusively with the human intellect. Though our reason aspires to answer metaphysical questions about the nature of things in themselves, it is incapable of doing so. However, reason is capable of surveying all possible knowledge, and as such can be applied in a self-critique. Kant recommends a new kind of metaphysics that uses reason to investigate the grounds and justification for human knowledge.
Thing in itself
Things in themselves (
Appearance
What we think of as "nature" is essentially a set of appearances. Appearances are sensations that have been structured by our faculties of sensibility and understanding in such a way that they appear to us in space and time and seem to follow certain laws and regularities. These appearances are caused by things in themselves, but are given form by our faculties.
Sensations
Sensations are the raw material of sense data. These are the impression things in themselves make on our senses. They are subsequently structured by our faculties of sensibility and understanding, but they come to us in a chaotic, simple form.