This is a short preview of the full episode.
On G.E. Moore's Principia Ethica, ch. 1 (1903); Charles Leslie Stevenson's "The Emotive Meaning of Ethical Terms" (1937), and Alasdair MacIntyre's After Virtue, ch. 1-2.
Is there such a thing as moral intuition? Is "good" a simple property that we all recognize but can't explain like yellow? G.E. Moore thinks that any attempt to define good in terms of properties like "pleasure," "interest," or "happiness" are doomed. Even if all pleasurable things were good, the word "good" still wouldn't mean "pleasant;" you could always sensibly ask, "but are those pleasant things really good?" This is Moore's "open question" argument, which expresses his objection to the "naturalistic fallacy," i.e. deriving an "ought" from an "is."
Stevenson agreed that "good" isn't reducible to any natural property; saying something is good is not to express a property about it at all. Instead, moral terms are tools we use to convince other people to like things that we like. This tendency of the word "good" to elicit such a response is part of what Stevenson calls its "emotive meaning."
MacIntyre thinks that this emotivism now pervades our current uses of ethical language. Because Moore is successful in debunking all the ethical theories that rely on natural facts (and supernatural ones too) to ground morality, we're left with no grounding at all, and people like Moore who pretend to be using intuition to discover primal moral facts are really just expressing their own preferences. The same goes for ethical theorists whose key terms don't hold up to scrutiny: when someone justifies an action by referring to a fiction like "greatest happiness," "natural rights," or "the dictates of reason," he is just, again, expressing his preferences; these bogus theories just serve to mask what's really going on. We'll give MacIntyre's positive account of how to ground morality (which is derived from Aristotle's) in episode 59.
End song: "When I Was Yours," by Mark Lint, 1997.