 Although the notion of an operational principle—a term that seems to originate with Polanyi (1958)—is central to engineering design, no single clear-cut definition of it seems to exist. The issue of disentangling descriptive from prescriptive aspects in an analysis of the technical action and its constituents is therefore a task that has hardly begun. This task requires a clear view on the extent and scope of technology. If one follows Joseph Pitt in his book Thinking About Technology (1999) and defines technology broadly as ‘humanity at work’, then to distinguish between technological action and action in general becomes difficult, and the study of technological action must absorb all descriptive and normative theories of action, including the theory of practical rationality, and much of theoretical economics in its wake. There have indeed been attempts at such an encompassing account of human action, for example Tadeusz Kotarbinski’s Praxiology (1965), but a perspective of such generality makes it difficult to arrive at results of sufficient depth. It would be a challenge for philosophy to specify the differences among action forms and the reasoning grounding them in, to single out three prominent fields of study, technology, organization and management, and economics.