Brouwer’s dissertation contains both the germs of his topological and his foundational work. We concentrate here on the latter. The extraordinary rich thesis contains comments and critique on his contemporaries, and a novel approach to many foundational issues. Between the lines one ﬁnds the genesis of the continuum and the natural numbers via the ur-intuition, the constructive interpretation of logic, choice sequences, and a precise discussion of the language, logic, and mathematics levels. The present paper provides a survey of the material and comments on Brouwer’s innovations.