Genology of the Four Relations

Though going back to Aristotle and porphyre Tyrien,the matter of the four relstions between two concepts, as a distinctive division, is one of the most important innovations in Arabic logic. This devision, for the first time, appeared in Farabi, Ghazali, Razi, and Khunaji in different forms. The devisions of the first three sufferred respectively from the fallacies of ‘non-coherency’, ‘non-exclusivity’ and ‘overlap of the sub-classes of the division’, so the later Arabic logicians didn’t accept them; thus Khunaji’s devision, laking all the fallecies, found its way to the pedagogical books and and established itself in Arabic logic up today. Although it has encountered important paradoxes from the very outset, it could resist all of them and reach its today firmed and established position in Arabic logic. In this paper, we explore the background of the four relations and determine each logician’s contribution in developing the subject.