G.E. Moore’s open question arguments (OQAs) have been targeted by unsympathetic philosophers for close to a century. Perhaps the most serious criticism directed towards Moore’s OQAs is that they beg the question against targeted theories. After presenting an OQA extracted from §13 of Principia Ethica, I lodge this question-begging objection before articulating Moore’s autobiographical efforts to mitigate its force. I then suggest that Moore’s OQAs are incomplete, awaiting the final stage of construction, an explanation of the ‘open question’ phenomenon—the inclination (...) of many philosophers to endorse the central premises of Moore’s OQAs. After a brief investigation of noncognitivist attempts to explain the phenomenon, I propose a semantic explanation, a cognitivist explanation that commits its proponents neither to mysterious nonnatural properties nor to perilous positions regarding the paradox of analysis. I conclude by arguing that Moore’s completed OQAs are successful, but his deployment of them in efforts to refute metaethical naturalism, even analytic or semantic versions, is not. (shrink)