In philosophy, idealism has two meanings. First as objective or metaphysical idealism versus naturalism, and second as subjective or epistemological idealism versus epistemological realism. Idealism in the former sense concerns the priority of spirit over matter or spiritualism, while in the latter it implies the refutation of materiality of the objects of sensual knowledge. Out of objective idealism and naturalism, Muslim philosophers put forward a third view. On the one hand, they accept the reality of material beings, and on the other, some of them, like Sohravardi and Mulla Sadra, though different from Plato, accepted the existence of the Ideas. In the realm of epistemology, Muslim philosophers are realists; that is, the subjective idealism is denied by them. Their confrontation with subjective idealism was initially started by criticizing sophistry and then, appeared in Tabatabaei and Muthahhari and Mesbah,s works in the form of criticizing sophistry and idealistic thought and defending realistic foundations of Islamic philosophy in the field of knowledge