Process philosophy is a philosophical and metaphysical system developed by Alfred North Whitehead, described in his book Process and Reality. Whitehead was a philosopher with a neoclassical theistic point of view, and was also a logician/mathematician with a scientific point of view. He understood the physics of his day (in terms of relativity theory and quantum mechanics) as fully as anyone, even to the point of developing a Theory of Relativity similar to Einstein’s. He incorporated a scientific worldview into the development of his philosophical system.
Process philosophy suggests that fundamental elements of the universe are occasions of experience. According to this notion, what people commonly think of as concrete objects are actually successions of these occasions of experience. Occasions of experience can be collected into groupings; something complex such as a human being is thus a grouping of many smaller occasions of experience. According to Whitehead, everything in the universe is characterized by experience (which is not to be confused with consciousness); there is no mind-body duality under this system, because "mind" is simply seen as a very developed kind of experiencing. However, Whitehead is not an idealist in the strict sense. Whitehead's ideas were a significant development of the idea of panpsychism (also known as panexperientialism, due to Whitehead’s emphasis on experience).
Whitehead’s philosophy resembles in some ways the concept of monads first proposed by Leibniz. However, unlike Leibniz’s monads, Whitehead’s occasions of experience are interrelated with every other occasion of experience that has ever occurred before. Inherent to Whitehead’s conception is the notion of time; all experiences are influenced by prior experiences, and will influence all future experiences. This process of influencing is never deterministic; an occasion of experience consists of a process of prehending other experiences, and then a reaction to it. This is the process in process philosophy. Because no process is ever deterministic, free will is considered essential to the nature of the universe.
Process philosophy gives God a special place in the universe of occasions of experience. God encompasses all the other occasions of experience but also transcends them; thus Whitehead embraces panentheism. Because free will is inherent to the nature of the universe, God is not omnipotent in Whitehead’s metaphysics. God's role is to offer enhanced occasions of experience. God participates in the evolution of the universe by offering possibilities, which may be accepted or rejected.