Kant's three metaphysical concepts

I. Three metaphysical concepts
Self
The Cosmos
God
We can’t really discover these by pure reason, because pure reason operates within experience. He calls these transcendental illusions, but it doesn’t follow from that that they don’t exist. They’re just not objects of theoretical knowledge.

II. The Self
Kant thought that every thought or judgment is preceded by the “I think.”
However, the self is not known as a substance. The self we discover in experience is the empirical self, the self as it appears to us. Psychologists can study this self.
The self as it is in itself is called the “transcendental ego” or “transcendental unity of apperception.” This is not known through experience, either introspective or through scientific investigation.

III. The World as a Totality
We can add up all the finite experiences of the world and call it a cosmos.
However, when we attempt to theorize about this as if it were reality as it is in itself, we end up with contradictions. Did the world have a beginning in time? Is it spatially limited? Can it be divided into basic elements? Are some events free and undetermined? Is there a necessary being?
If we think we know the world as it is in itself, we can reason ourselves to opposite answers on this, and these Kant calls antinomies.

IV. Kant’s sympathy for metaphysics
Kant thought that if there is no God and no free will, moral ideas lose all their validity.
However, that doesn’t mean that we can reason from the world to these ideas. This would be to use concepts designed to put experience together and extend them beyond the world of experience.
However, these ideas could be the product of “intellectual presuppositions and faith.”