A theory may have a bearing on action either because it provides knowledge regarding the objects of action, for example, machines, or because it is concerned with action itself, for example, with the decisions that precede and steer the manufacture or use of machines. A theory of flight is of the former kind, whereas a theory concerning the optimal decisions regarding the distribution of aircraft over a territory is of the latter kind. Both are technological theories but, whereas the theories of the first kind are substantive, those of the second kind are, in a sense, operative. Substantive technological theories are essentially applications, to nearly real situations, of scientific theories; thus, a theory of flight is essentially an application of fluid dynamics. Operative technological theories, on the other hand, from the start are concerned with the
operations of men and man-machine complexes in nearly real situations; thus, a theory of airways management does not deal with planes but with certain operations of the personnel. Substantive technological theories are always preceded by scientific theories, whereas operative theories are born in applied research and may have little if anything to do with substantive theories-this being why mathematicians and logi- cians with no previous scientific training can make important contribu- tions to them. A few examples will make the substantive-operative dis- tinction clearer.