Whitehead brings a theory of everything, it being cosmology after all, by offering a Philosophy of the Organism to explain how reality is a passage at the knife edge of now. Rather than taking the substance-predicate at face value, Whitehead exposes the contradictions in the Cartesian thought and demonstrates how conceptions of interaction and atomism are not exclusive. Stunning in its breadth and ability to explain what Whitehead sees as the composition of our world Process and Reality (relatively) simply is an absolutely seminal piece of modern philosophy.
The Philosophy of the Organism looks at the manner in which objects become concretized and therefore incorporate other prior objectifications in their composition. Whitehead cleaves reality into two - interdependent - types of entities: the actual and the eternal. Actual entities, also known as occasions, are "the final real things" the world is made of, but are themselves also nexus. The manner in which different entities interact with one another is called their prehensions: without their prehensions actual entities are unrecognizable, and with an understanding of the actual entities prehensions become meaningless. Throughout this it is of paramount importance to keep in mind that actual entities are never to be conceived as unchanging subjects: the moment they are come together into a public the object has begun its perishing into a new process of becoming. Eternal objects participate in the actual by the means of ingression. Eternal objects are the mode of possibility of any concrescence, but are not realized except in the actual. Being able to truly pick apart what Whitehead means by this and the implications, even after a close reading of Process and Reality, is far from straight forward.
There is much more in this work than can be covered here. What seems of crucial importance is to include Whitehead's conception of the antithesis. Whitehead's Philosophy of the Organism cannot be separated from his conception of novelty in the universe, or, what he calls God. For the Philosophy of the Organism recognizes that all things are constantly engaged in the emergence of creation and dying, and that the emergence of new things can never fully be understood in terms of their compositional entities. That the universe is both fluid and static, that the dynamic, to meaningfully exist, must be grounded is, for Whitehead, apparent. That which is not, but all that is novel in the process of becoming, is the crux of existence.
"In the inescapable flux, there is something that abides; in the overwhelming permanence, there is an element that escapes into flux. Permanence can be snatched only out of flux; and the passing moment can find its adequate intensity only by submission to permanence." p. 478
