Ontologic Versus Epistemologic: Some Strands in the Development of Logic, 1837–1957

Traditionally the subject matter of logic comprised judgements and inferences, that is, the products of certain (mental) acts. Indeed, Thomas Aquinas even characterized logic as the study of terms in ‘the second intention’, that is, such terms that themselves have mental entities as their intention, examples being the term ‘term’, the term ‘judgement’ and the term ‘inference’. Today, on the other hand, authoritative elementary text books in Logic make no mention of products of mental acts: the acting logical subject that has to draw the inferences in question has, as it were, been squeezed out of the province of logic.