Traces of Kant's main ideas can be found in hand written notes that he used to prepare before delivering his lectures. It is clear from these pages how Kant reached the conclusion that reason acting on its own could not establish epistemologically valid results and that cognitively valid findings must be confirmed by experience. A non-verifiable proposition does not refer to anything, Kant believed. Having made these observations the author focuses on discrepancies between some of Kant's essential premises., e.g. the discrepancy between status and functions of the intellect and senses, or between a priori truths and transcendentalism. Following Kant the author argues that without direct insight pure reason is empty and cannot serve as a fundamental cognising faculty. Less clear is the status, unity and functions of self-consciousness (the self or the subject). The unity of the subject emerges as a result of the application of categories (synthesis) and is not a raw datum. This makes several contentions of Kant doubtful. The author believes that Kant drew his inspiration for the development of the tables of categories from the Emile by Rousseau. In conclusion the author says that the main achievement of Kant is to be found in the showing that the self, truth and objective validity of cognising are intimately connected and inseparable.