Among the truly outstanding philosophers of the twentieth century, Alfred North Whitehead holds the unenviable status of being the most neglected. Before the outbreak of the Second World War he was widely acclaimed as one of the great thinkers of the times. After that tragic event, the philosophical world in both Britain and the USA changed radically. Academics now perceived themselves as professionals with their own field of expertise; Whitehead's metaphysical writings, which are full of daring speculations into the ultimate nature of things, could hardly exert any great attraction on philosophers hypnotised by the fabulous minutiae of logic and linguistic analysis.

Because of the oblivion into which it fell in the second half of the last century, Whitehead's process metaphysics remains comparatively little known. It is ignored, rather than rejected on philosophical grounds. This is regrettable, for Whitehead dealt in unconventional fashion with questions that are at the centre of contemporary debates, especially in ontology and the philosophy of mind. Some prominent analytic philosophers working in these fields are even travelling intellectual paths closely resembling Whitehead's own, apparently without fully realising it.

This book aims at making Whitehead's complex system accessible to a wider audience than it currently enjoys. It is by no means to be regarded as a complete interpretation of his worldview. Nevertheless, an effort has been made to elucidate all the basic principles that ground his vision and, most importantly perhaps, the problems to which his philosophy is supposed to provide an answer. At the same time, and following Whitehead's own practice, I have tried to show how he reached his sometimes very counter-intuitive conclusions by way of dialogue with the great masters of the past – Plato and Aristotle, but also early modern philosophers like Descartes, Newton, Locke, Hume and Spinoza. A prominent place in the following reconstruction is occupied by Leibniz, who is, together with Plato, Whitehead's true philosophical hero.

There are deep philosophical motivations behind Whitehead's engagement with such great figures. As he explains in his magnum opus, Process and Reality (1929), our thinking is held captive by old ideas unconsciously held. What philosophy stands in need of is a conceptual revolution – a critique of tradition that would also enable us to develop a radically new way of conceiving of the world and our place in it.