 Following Russell, I call this the Barren Tautology Argument or BTA (RoE: 100/Papers 4: 572). The idea is that “good” cannot be synonymous with any naturalistic “X”, if “X things are good” is supposed to be a reason for action rather than a “barren tautology”. So for example, if “good” just means “pleasant” then “Pleasant things are good” is a barren tautology (equivalent to “Pleasant things are pleasant” or “Good things are good”) and cannot provide us with a reason for the pursuit of pleasure. Only if “goodness” and “pleasure” are not synonymous, can “Pleasant things are good” provide an intellectual incentive for the pursuit of pleasant things. This argument crops up at PE: §11 (though variants of it recur throughout the first four chapters (PE: §§14, 24 &amp; 26):