ABSTRACT
In the early 1930s there was prevalent, among scientifically minded philosophers, the view that semantic notions such as the notions of truth and denotation were illegitimate: that they could not or should not be incorporated into a scientific conception of the world. But when Tarski's work on truth became known, all this changed. 'As a result of Tarski's teaching, I no longer hesitate to speak of "truth" and "falsity",' wrote Popper;l and Popper's reaction was widely shared.2
