ABSTRACT
THE psychologists, when they discuss reasoning at all (and some of them hardly give it passing mention), take the ground that the kind of reasoning that interests them is something very different from the cut and dried formulae of the logician. The reason for this quarrel between two honourable branches of science is simply, of course, that the psychologist has the inveterate habit of including in his term reasoning the search for what I have called (a technical term) the “adequate” premises—which is half the battle, to be sure, when one is engaged in thinking out a solution to real difficulties. The pure logician, on the other hand, cares nothing for this aspect of the matter—he is concerned only with the validity of structures of premises. I propose to use the term practical logic, in a technical sense, for the psychologist’s logic, and to call that of the logician theoretical logic, or pure logic. This simple device of giving two names to two different things ought to have the effect of modifying the contemptuous terms in which the psychologists sometimes discuss the logicians.
