call for reconstruction of metaphysics. The process metaphysics elaborated in Process and Reality posits an ontology which is based on the two kinds of existence of an entity, that of actual entity and that of abstract entity or abstraction, also called 'object'. Actual entity is a term coined by Whitehead to refer to the entities that really exist in the natural world. For Whitehead, actual entities are spatiotemporally extended events or processes. An actual entity is how something is happening, and how its happening is related to other actual entities. The actually existing world is a multiplicity of actual entities overlapping one another. The ultimate abstract principle of actual existence for Whitehead is creativity. Creativity is a term coined by Whitehead to show a power in the world that allows the presence of an actual entity, a new actual entity, and multiple actual entities. Creativity is the principle of novelty. It is manifest in what can be called 'singular causality'. This term may be contrasted with the term '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 recognizes 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 till 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 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, qua actual entities, with a single exception. For example, for Aristotle, the actual entities were the substances, such as Socrates. Besides Aristotle's ontology of substances, another example of an ontology that posits actual entities is in the monads of Leibniz, which are said to be 'windowless'. Whitehead's actual entities For Whitehead's ontology of processes as defining the world, the actual entities exist as the only fundamental elements of reality. The actual entities are of two kinds, temporal and atemporal. With one