Cassirer and Self-Consciousness

In Cassirer's account, the earliest manifestation of self-consciousness is the possessive 'my'--even 'I go' is initially expressed as 'My going'. Eventually, the dynamic 'I' splits off, and, ultimately develops into 'I think'. But, the latter, which is plainly derived from Kant's theory, is an impersonal function. Thus, like Kant, Cassirer does not explain how the personal 'my' is derived from an 'I' that is as impersonal as a thinker as it is as an object of possession at the earlier phase. Unlike Kant, Cassirer goes no further. For, Kant's subsequent Pure Principle of Practical Reason, aka 'the Categorical Imperative', creates a new 'I', i. e. the subject of 'I will', which, furthermore, is the bearer of personhood. Not merely does Cassirer relatively neglect this dimension of the Kantian System, but in the absence of a derivation of a 'me' consciousness, he would seem to have difficulty explaining how an 'I' can understand that it is being addressed in 'act only on that maxim which you can at the same time will to be a universal law'.