Is my mind transparent to me?
On the axis: The enigma of consciousness · one's own mental life
I believe I know better than anyone what I think and feel. But the mind may exceed what it perceives of itself: what if introspection told, after the fact, a story about a mental life that largely escapes it?
Justification
The argument rests on a principle: what I clearly and distinctly conceive as able to exist apart really exists apart, since God could create it so. Now I can conceive my mind, pure thinking thing (res cogitans), with nothing corporeal attributed to it, and body, pure extension (res extensa), with no thought. My essence is therefore to think, and the mind is really distinct from the body, a substance of another nature than the brain. This substance dualism breaks with the Aristotelian soul, form of a body, and at one stroke frees matter for a purely mechanistic physics; yet it bequeaths the problem, which Descartes will struggle to solve, of their union and interaction.
Meditations on First Philosophy, VI
Justification
The self is a substance, a thinking thing, whose existence is grasped immediately in the cogito and whose identity depends on neither body nor memory. This is a substantialism of the subject, which also secures the soul's immortality.
Meditations on First Philosophy, II · Discourse on Method, IV
Justification
The self is a monad, a simple, indivisible substance whose individual notion includes once and for all everything that will ever happen to it. Personal identity is thereby secured by the permanence of this substance, a marked substantialism. Leibniz nonetheless grants a role to memory and the continuity of consciousness (apperception), adding a nuance of psychological continuity.
Monadology, §1-3 and §14 (the monad, simple substance; perception and apperception) · Discourse on Metaphysics, §8-9 (the individual notion of each substance)
Anchors: Descartes · Leibniz · Freud
leads to: Nature of the self (One self or many?)