Khunaji and his companions get influence from Fakhr al-Din Razi and classified quantified propositions into two kinds: factual and external. Abhari added the third kind which was named mental. Tusi and his companions refuted Khunaji’s viewpoint. Analysis and explanation of the historical development of classification of predicative proposition into factual, external and mental is the problem of this research. In the shade of analysis and historical explanation of this classification would be clear that this problem has two classifications under one name: bipartite and triadic. The present article is an attempt to study the contribution of two-fold logicians of the 7th century to the development of logic.
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