Historical Movement of the Four Relationships in Islamic Logic

This essay studies Nisab Arba` or the relationships between universal concepts from historical aspect. The great pre-Avicennian logicians as like as Aristotle and Farabi، and also Avicenna himself didn’t pay attention to the issue of the four relationships between universal concepts with respect to their extensionality and comparability. Ghazali was the first philosopher who raised the above issue with intellectual restriction، without contrast relation. Afzal al-din khunaji and siraj al-din Urmawi–following him– were the first post-Ghazali logicians that explained the four relationships in the current forms، and the relations between their contraries.