Ethics: Inventing Right and Wrong

Mackie's book opens with the claim that there are no objective values and defends it in the most influential first chapter in modern meta-ethics. Ordinary moral judgements, he argues, do purport to describe objective, action-guiding facts, so the view is an error theory: those judgements are systematically false. He supports it with the argument from relativity, that moral disagreement is better explained by different ways of life than by some people misperceiving objective values, and the argument from queerness, that such values would be metaphysically and epistemically unlike anything else. He also explains why we tend to project our attitudes onto the world. The rest of the book then asks what morality we should construct once this is accepted, discussing universalisability, the function of morality in countering limited sympathies, utilitarianism, rights, and the bearing of religion and determinism on ethics.

It states the case for moral scepticism more clearly and forcefully than any other book, which is useful whether you accept it or are trying to answer it.