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 is Philip Stratton-Lake on G. E. Moore's Principia Ethica. Moore's book had a revolutionary impact on moral philosophy. Moore argues for moral realism – the doctrine that ethical judgements can be true or false – but against all forms of natural reductionism – the view that good can be defined in non-moral, natural, terms. The latter claim is the “naturalistic fallacy”, and the fallacy is exposed by directed attention to positions such as hedonistic utilitarianism where “good” is defined in terms of pleasure. Moore uses the “open question” argument to refute all such reductions to some natural property x as giving the definitional meaning of good. If they really gave the definition of “good”, then it would not make sense to ask “Is x good?”, for one would be asking “Is good good?”. But the question always does make sense. Moore defends a form of consequentialism according to which we should, morally speaking, aim at things that are good.