Abstract

Although the concepts of necessity and possibility are inseparable concepts of metaphysics, the empiricist philosophers have traditionally challenged them. In the twentieth century, these criticisms were proposed by Quine in a new form. However, the emergence of the concept of possible worlds in semantics of modal logic made the belief that the challenge of empiricism may be defeated. In explaining the nature of possible worlds, there are two different approaches. Some philosophers believe that the concepts of possible worlds, necessity, possibility, essential, and accidental are members of a network. On the other hand, some philosophers use the reductive nominalism approach in describing the modal notions and reduce the other modal notions to the concept of possible worlds. In this article, after proposing Plantinga's criticism, as an outstanding representative of the first approach to the reductive nominalism, his standpoint to the nature of possible world will be discussed. The key concept in his thought is the state of affairs. He considers the possible world as a maximal state of affairs. Then, it will be shown that Plantinga's conception of the possible worlds can be adapted to the concept of Nafs-al-Amr in Islamic philosophers' view, in spite of obvious differences between them.