But, in consideration of the fact that a completely novel type of mathematical analysis had shot up in a mighty theoretical-technical development during the nineteenth century, and because of the need of making clear the still utterly confused logical sense of this analysis, I saw yet a third and highest task for a formal logic or formal theory of science. It is announced, in the title of § 69¹, as the theory of possible forms of theories or (correlatively) the theory of multiplicities.