This paper sketches a historical account of interdisciplinarity. A central claim advanced is that the modern array of scientific and humanistic disciplines and interdisciplinarity emerged together; both are moving targets, which must therefore be studied historically in relation to one another as institutionalized practices. A second claim is that of a steadily increasing complexity; new fields emerged on the boundaries of existing disciplines beginning in the late nineteenth century, followed by multi- and transdisciplinary initiatives in the twentieth, and finally transdisciplinary programmatic research in the late twentieth and early twenty-first centuries. The latter two phases in this development have been driven primarily by funding agencies seeking to move the sciences in particular directions deemed socially or politically desirable (in dictatorships as well as democracies), while the existing disciplines remained in place and new ones came into being. Such policy initiatives have transformed both disciplinarity and interdisciplinarity in unanticipated ways. The question whether multi- or transdisciplinary arrangements produce epistemically better science or scholarship appears not to have been raised, let alone examined, by the policy actors driving their creation.