 Let us posit that metaphysical idealism need not be the counterintuitive view that all that exists is, simply, mental. To call a view idealist it is sufficient merely that it hold that everything is dependent upon mind—a mind, or many minds. Idealists hold that the natures or forms of things are mind-dependent. Of course, such dependence is, in itself, counterintuitive, given that we generally take the physical world to have existence independent of minds. Contemporary prevailing wisdom holds that the direction of causal dependence goes in the opposite direction; the physical world in fact generates and sustains minds (using neurons to do so). Idealism says that ideas, or minds, are in one way or other behind, or prior to, all other forms of existence.