Reviewing Hume’s Objections to ‍the Demonstration of Necessity and Possibility Based on Avicenna’s Exposition

According to Avicenna’s exposition of ‍the demonstration of necessity and possibility based on the evidence of the subsistence of reality, an external being either is existent by necessity because of its nature, or has no necessity for existence and non-existence, and its existence is provided by a necessary being outside the chain of possible beings. Gottfried Wilhelm Leibniz has considered contingency as the possibility of doubt in propositions governing the reality, and the way to get rid of this doubt is to accept a necessary being that has given the world a necessity. When David Hume, considering Leibniz’s exposition, objects ‍the demonstration of necessity and possibility, he states that, firstly, merely possibility of doubt in external beings does not make the necessary being be confirmed because the same doubt applies to the necessary being; and, secondly, the concept of the necessary being is inconsistent: the necessity only describes the analytical propositions, and not the propositions governing the reality; therefore, one can cast doubt on the existence of a necessary being, which is not compatible with its being necessary. In this study, we aim at giving answers to these objections using the analytical-descriptive method by relying on the principles and foundations of Avicenna’s exposition, and state that, firstly, possibility means the lack of inherent necessity of external reality in relation to existence and non-existence, from which existence of necessary being can be understood; therefore, Leibniz has confused probable possibility and essential possibility, and that, secondly, the imputing necessity to an object in the capacity of a mental image and in the orbit of the primary predication does not entail its external realization to make it incompatible with the possibility of doubting its realization.