Principia ethica

Principia Ethica, published in 1903, is a seminal work in ethics that shifted the study of ethics from normative questions to issues of 'metaethics,' the study of ethical concepts.

Moore critiques conventional ethical theories and introduces the concept of the 'naturalistic fallacy,' which argues against conflating moral terms with natural properties.

The book distinguishes between questions related to the intrinsic goodness of things and those concerning the rightness of actions, emphasizing the importance of understanding what is meant by 'good' before attempting to define it.