Abstract

Despite its centrality for ethical theory, and the near-axiomatic status it enjoyed for years, the thesis that an Ought cannot be derived from an Is has not until fairly recently come in for close scrutiny. During this time, however, there has been a swing of the pendulum from the view of G. E. Moore, that no one in his right mind could deny the thesis, to that of some contemporary philosophers who speak as though no one in his right mind could affirm it. Predictably, the fact that traditional defenders of the thesis were not always clear about what they meant by it has meant that it has not always been clear what contemporary critics have been asserting when they deny it. Also predictably, this has meant that there has been no conclusive resolution of the issue.