The paper explores a claim made by Hermann Ulrich Kantorowicz in a historically signification pamphlet, which may in some respect well have prepared the intellectual ground for the American legal realist movement. The claim is that the legal science is a source of law. It is startling, to say the least, to find this claim articulated in the context of a piece of "sociological" jurisprudence. The paper then contrasts Kantorowicz's claim with the the parallel claim made by the historical school and concludes that the ideas articulated by its members - Georg Friedrich Puchta, in particular - were exceedingly more plausible. In order to understand this, however, it is necessary to conceive of all legal knowledge as a species of self-knowledge. This is the idea that the paper tries to make plausible and, indeed, to defend.