Abstract

In this article, I discussed how Ibn Sína defined “the converse ” and how later logicians conributed to his definations. For Ibn SínÀ have got two definations in the different works: KitÀb al-ShifÀ: al-ÚıyÀs versus al-IshÀrÀt which hold the record of “falsehood ” in the converse. This record didn’t exited in former logicians’ works : for example Aritotle and al-FÀrÀbí. But some later logicians accepted the defination of KitÀb al-ShifÀ: al-ÚıyÀs and the others accepted al-IshÀrÀt’s defination. However commentators of al-IshÀrÀt- Ùÿsí and Semerúandí- didn’t accepted the record of falsehood in the converse. According to them, this record was entered by scribes . On the other hand Ibn SínÀ used only terms of categorical proposition, not hypothetical propositions’ terms. Later logicians offers more general terms icluding both categorical proposition and hypothetical proposition