Full Idea
Kant insists that the 'I' of consciousness is purely formal, and does not carry with it any positive conception of the self as substance.
Gist of Idea
For Kant the self is a purely formal idea, not a substance
Source
report of Immanuel Kant (Critique of Pure Reason [1781], B406-/A398-9) by Michael Lockwood - Mind, Brain and the Quantum p.169
Book Reference
Lockwood,Michael: 'Mind,Brain and the Quantum:The Compound 'I'' [Blackwell 1991], p.169
A Reaction
We might agree that a self does not involve any awareness of the substance of which it is constituted, but it is hard to see why we might get so worked up about the past, present and future of something which is 'purely formal'.