No account that locates consciousness purely within individual representations (intrinsically self-conscious perceptions or perceptions of perceptions) can explain the identity of the subject across multiple acts of self-attribution.

Moreover, it might well be that the argument of §16 features a subtlety that obviates the need for actual co-consciousness. The text indicates that the argument crucially turns on the claim that only a priori synthesis – that is, synthesis by a priori concepts – can explain how I might represent the identity of my apperceptive consciousness (B133) or how I might represent the identity of the apperceiving subject (B135) for different elements of the manifold of intuition to which I can attach the