The point of departure in the paper is the problem of identification of the foundations of knowledge, its beginning and status in modern philosophy (Descartes, Leibniz, Wolff, Hume, Fichte, Chisholm, Shoemaker). The author undertakes an analysis of the position taken by Kant in the context of the problem of transcendental deduction of categories and its fundamental principle - the transcendental unity of apperception. He focuses on the connection between transcendental apperception with pre-predicative existence of pure consciousness and intellectual insight. Kant held that consciousness is a result of the self-referring operation of auto-reflection. This means that self-consciousness is not some kind of knowledge, nor is it any sort of mental content through which it would be possible to identify the subject.