In this paper I argue that G.E. Moore’s naturalism (combined with his sense-data theory) falls prey to the charge, leveled recently by Plantinga, that Moore doesn’t know whether his belief-forming mechanisms are functioning properly when he says he knows a pencil (or his hand) exists. Help from Alston may be sought in response to criticisms, but these are not sufficient to vindicate Moore’s form of naturalism.
Martin, Edward N., "On Behalf of the Fool: G.E. Moore and Our Knowledge of the Existence of Material Objects" (1996). Faculty Publications and Presentations. 61.