 It is one thing to say that thick concepts are a distinctive kind of evaluative concepts, another to say that this gives them distinctive philosophical significance not carried by thin concepts. Among various arguments which attribute distinctive significance to thick terms and concepts, two have been particularly influential: arguments concerning the “is-ought gap” and the distinction between facts and values, and the “anti-disentangling” argument. We’ll also briefly address questions bearing on the relative priority of thick and thin concepts in evaluative thought.