Abstract

One of the important problems of philosophy from the very beginning was how to prove the existence of the First Source of beings. The present research is a comparative study on the First Source from the viewpoint of Avicenna and Leibniz. Here, in the first place, we will consider the Proof of Truthful of Avicenna and Leibniz’s proof of the Principle of Sufficient Reason. In the second place, the causation of the First Source is studied in the form of three questions. The conclusion of this research is that both of Avicenna’s and Leibniz’s proofs are based on the argument of contingency and necessity, but Avicenna’s proof refers to the existence in itself, while Leibniz’s one is based on the division of entities. First cause, in the view point of Avicenna, is the efficient cause but it is, for Leibniz, a source of efficient and final causes. The First Source, for both Avicenna and Leibniz, is true (or necessity) and conservative cause.