Process and Reality is a book by Alfred North Whitehead, in which the author propounds a philosophy of organism, also called process philosophy. The book, published in 1929, is a revision of the Gifford Lectures he gave in 1927–28. Whitehead's Process and Reality Whitehead's background was an unusual one for a speculative philosopher. Educated as a mathematician, he became, through his coauthorship with his student and disciple Bertrand Russell and publication in 1913 of Principia Mathematica, a major logician. Later he wrote extensively on physics and its philosophy, proposing a theory of gravity in Minkowski space as a logically possible alternative to Einstein's general theory of relativity. Whitehead's Process and Reality is perhaps his philosophical master work. The following is an attempt to provide an accessible outline of some of the main ideas in Whitehead's Process and Reality, based on the book itself, but guided by a general reading of secondary sources, especially I. Leclerc's Whitehead's Metaphysics. An Introductory Exposition. Whitehead often speaks of the metaphysics of Process and Reality as 'the philosophy of organism'. The cosmology elaborated in Process and Reality posits an ontology based on the two kinds of existence of entity, that of actual entity and that of abstract entity or abstraction. The ultimate abstract principle of actual existence for Whitehead is creativity. Actual existence is a process of becoming, and “'becoming' is a creative advance into novelty”. It is manifest in what can be called 'singular causality'. This term may be contrasted with 'nomic causality'. An example of singular causation is that I woke this morning because my alarm clock rang. An example of nomic causation is that alarm clocks generally wake people in the morning. Aristotle recognises singular causality as efficient causality. For Whitehead, there are many contributory singular causes for an event. A further contributory singular cause of my being awoken by my alarm clock this morning was that I was lying asleep near it until it rang. An actual entity is a general philosophical term for an utterly determinate and completely concrete individual particular of the actually existing world or universe of changeable entities considered in terms of singular causality, about which categorical statements can be made. Whitehead's most far-reaching and profound and radical contribution to metaphysics is his invention of a better way of choosing the actual entities. Whitehead chooses a way of defining the actual entities that makes them all alike,