The appealing principle that you can't get an ‘ought’ from an ‘is’, sometimes called Hume's Guillotine , faces a well-known challenge: it must give a clear account of the distinction between normative and descriptive sentences while dodging counter-examples. I argue in this paper that recent efforts to answer this challenge fail because the distinction between normative and descriptive sentences cannot be described well enough to be of any help. As a result, no version of the principle is both true and (...) adequate. Yet a different principle—that no normative terms are synonymous with any descriptive terms—can satisfy much of the motivation we had for defending Hume's Guillotine in the first place. I show briefly how this second principle can explain why is-ought arguments are invalid, block some attempted deductive justifications of beliefs with normative terms, and create an explanatory advantage for moral non-cognitivism. Just so, giving up Hume's Guillotine is the prudent thi.. (shrink)

Since the time of Hume, many philosophers have thought it impossible to deduce an ‘Ought’ from an ‘Is,’ or in general to deduce ‘ethical sentences’ from purely ‘factual sentences.’ This is the thesis of the logical autonomy of ethics. I consider a more recent argument by Toomas Karmo in support of the autonomism, but show its limitations in the context of justification skepticism about ethics.