Twofold Propositions, Factual-External, and Their Function in Demonstrative Argument

The present article intends to explain, the epistemological function of factual and external propositions in demonstration figure in the shade of studying the logical conditions and rules of these propositions. About factual and external propositions various viewpoints have investigated, but the outlook in the present article is based on the difference of these propositions in the relation between the confirmation of the subject and the confirmation of the predicate. This relation in the factual proposition is essential but in the external proposition is accidental. This article urges the belief that the conditions of argument propositions are clearly found in the factual proposition. So only the factual proposition can be used in islamic logical method of scientific thought.