 Abelard’s main objection to the resemblance theory is that mental images qua images, like any sign, are inert: they require interpretation. A sign is just an object. It may be taken in a significative role, though it need not be. Abelard notes that this distinction holds equally for non-mental signs: we can treat a statue as a lump of bronze or as a likeness. Mental images are likewise inert. For a sign to function significatively, then, something more is required beyond its mere presence or existence. But the resemblance theory doesn’t recognize the need to interpret the mental image as an image, and thereby mistakenly identifies understanding with the mere presence of a mental image in the mind. Abelard concludes that mental images have only an instrumental role in thought, describing them as “intermediary signs of things” (intersigna rerum). Intentionality derives instead from the act of attention (attentio) directed upon the mental image. Proof is found in the fact that that we can “vary the understanding” simply by attending to different features of the mental image: the selfsame image—say, a fig tree—can be used to think about this very fig tree, or trees in general, or plant life, or my lost love with whom I sat under it, or anything whatsoever. There is no intrinsic feature of the mental image in virtue of which it is about any given thing; if there were, Abelard notes, we could determine by inspection what a sign is about—but we can’t. Mental images, therefore, can’t explain the intentionality of understanding, because their role is merely instrumental. We think with them, and cannot avoid them; but they do not explain intentionality.