Whitehead was Russell’s tutor in Cambridge, where he was Fellow of Trinity from 1884 to 1910, when he moved to London, and then to a chair of philosophy at Harvard in 1924. He collaborated with Russell on Principia Mathematica (1910–13). His own philosophy is an attempt at a systematic metaphysics built in the light of modern logic and science. Whitehead was impressed by the scientific concept of a flux or field of force and energy. Disliking both the atomism of the Newtonian world view, and that of the Humean analysis of experience into distinct perceptions, he sought to analyse such atoms in terms of overlapping sets of larger processes. His ‘method of extensive abstraction’ is that of defining an object such as a point in terms of nested volumes of space; similarly events become nested processes. The general ordering of the processes of the world is the primordial nature of God, represented as the principle of concretion whereby actual processes emerge. His Enquiry Concerning the Principles of Natural Knowledge (1919) and The Concept of Nature (1920) are considerably more accessible than the later Process and Reality (1929).