Abstract

The concept of necessity and its conceptual relation to permanence in modal logic is one of the most difficult topics to understand. Sometimes Ibn Sina regards necessity as permanence which is a part of necessity and sometimes regards it as more special than permanence. But necessity in Aristotle's view is the way a thing is as it is and can not be otherwise. The concept of immanance is the endurance of predicate in subject during the time, whereas necessity means the impossibility of separation of predicate from subject in certain conditions. By this analysis necessity is subordinate to permanence, is conditioned by continuity and is equivalent to the conditions of existing thing. According to Ibn Sina only necessary propositions have a special usage in exact sciences. Also, Aristotles considers the propositions which the relation between their subject and predicate is based on possibility as lacking scientific value. Later the separation of necessary and scientific in possible statements as the separation of analytic and synthetic propositions and the kinds of predication was propounded. Suhravardi regards necessity as the genus of a threefold modalities. In this view all logical propositions are self–evident. Spinoza in a similar way by stressing the identification of necessity and permanence regards the necessity as the condition of existence and considers possibility the result of nonrecognition of necessary system of the world.