This thesis deals with 'the principle of the unity of transcendental apperception' which is regarded as the key of the transcendental deduction of the categories in the Critique of Pure Reason. My thesis focuses on the logical aspect of the apperception principle in the B-Deduction. I argue that the apperception principle must be read as an analytic proposition in the B-Deduction. This implies that the apperception principle is a premise of the whole argument of the Deduction. Such an interpretation has at least three advantages over the other competing ones. First, it doesn't distort Kant's own words. Secondly, it can lead us to a meaningful reading of the B-Deduction considering its aim. Finally, it gives a reading coherent with the Paralogisms which are most closely related to the account of the apperception in the Critique. In the B-Deduction, the principle can be restated as follows: 'The act of the thought of the discursive understanding requires that each and every representation, which consists of a synthetic unity of representations, namely a single complex thought, must be connected in such a way that they could be ascribed to a single subject'. As Kant himself says in the B-Deduction and the Paralogisms, this normative statement is an analytic proposition which has a subject concept of the discursive understanding or thought and predicate concepts with rich contents followed by the analysis of the subject concept.