Al-vahed Rule from the Pperspective of Thomas Aquinas and Mulla Sadra

The rule of oneness (Al-vahed), as one of the most important philosophical rules, has always been considered by philosophers in order to explain the origin of the multiplicity of the universe from one. Most philosophers accepted its provisions, and some theologians denied it. Acceptance of the Al-vahed rule and belief in a single origin for all multiple beings leads the philosopher to the question of how to issue multiplicity from God, who is in all respects one. Meanwhile, Thomas Aquinas and Mulla Sadra also expressed their views on it based on their philosophical and ontological foundations. How many beings originated from a simple unit preoccupied the minds of both, and they, like other philosophers, had to find a way to do so. This article intends to study the works of Thomas and Mulla Sadra and the commentators and researchers in an analytical and research manner to examine the views of two philosophers on the Al-vahed rule to determine whether they both believe in the principle of the rule? What are the reasons for rejecting or accepting the rule in their opinion? How do each justify the emergence of plurals from the unit? Thomas ontologically denies the rule and criticizes those who believe in it. But Mulla Sadra, by accepting the principle of the rule, has restored it and based on his philosophical foundations, has presented a new plan of it.