 While many have focused on the development of quantifiers, it is quite noteworthy that Tarski drew our attention to the importance of the algebra of relations in his 1941 paper “On the Calculus of  Relations”.[20]  Just as Peirce did in his DNLR (1870) paper, Tarski acknowledges De Morgan’s contribution: It is De Morgan who first realized the necessity of representing relations as well as qualities and struggled over the limits of traditional logic. And Tarski gives full credit to Peirce in terms of solid advance over the calculus of relations.