Although there is no clear-cut doctrine of the subject in the work of Georges Canguilhem, nevertheless there is a sense in which the subject functions as a kind of operator in his work. This article delineates three aspects of such an operative function: a quasi-ontological discontinuity separating the living from the non-living; a discontinuity separating technique from science; and an ethical discontinuity that can be exemplified in the case of medicine. It is at these points of discontinuity that the notion of the subject effectively comes into operation in Canguilhem's work.