G.E. Moore (1873-1958) was a British philosopher (seen center here), who alongside Bertrand Russell and Ludwig Wittgenstein in the early twentieth century at Cambridge University, was a key protagonist in the formation of the analytic tradition during the twentieth century. 

This extract from OUP’s Analytic Philosophy: A Very Short Introduction explores Moore’s concern with the attempt to define “good’”— a key theme of Moore’s major work, Principa Ethica.

The central question of Principia Ethica is ‘What is good?’, and Moore’s main claim is that ‘good’ is indefinable, or, as it might also be put, that goodness is unanalysable and hence has to be regarded as a simple quality. His main argument for this is the ‘open question argument’, as it has come to be called. Consider a possible definition of ‘good’, say, as ‘that which we desire to desire’, which Moore himself takes as one of the more plausible. It seems, though, that we can quite genuinely ask ‘Is that which we desire to desire good?’

G.E. Moore

Read the rest of this chapter ”Do You Know What I Mean?“.