The works in the Central Works of Philosophy volumes have been chosen because of their fundamental importance in the history of philosophy and for the development of human thought. Other works might have been chosen; however, the underlying idea is that if any works should be chosen, then these certainly should be. In the cases where the work is a philosopher's magnum opus the essay on it gives an excellent overview of the philosopher's thought.

Chapter 1 by Janet Broughton introduces Descartes's Meditations on First Philosophy, which is usually taken as marking the beginning of modern philosophy. Descartes takes an intellectual journey, that is both logically rigorous and psychologically convincing, moving from sceptical subjectivity to establishing that there may be objective and certain knowledge. He also seeks to determine the ultimate nature of reality, and concludes that it can be divided into unextended consciousness or thought, and unthinking extended matter. The overall aim is to set aside the contingent aspects of our perspective on the world and so arrive at an objectively true conception of reality.

Chapter 2 by Steven Nadler presents Spinoza's Ethics. This work aims to connect at a fundamental level metaphysics and ethics. Spinoza sets out to show that ultimately there can be only one substance: something that includes within itself the full explanation for both its nature and existence. He calls this “God”, but it has none of the features of a traditional personal God, and instead God is identified with the universe as a whole. There can only be one possible universe, and occurrences within it unfold with necessary logical inevitability.