  We still need to clarify in what sense existence can be said to be concomitant with essence. Being has access to essence from the outside, in the sense that it does not strictly belong to the essential nature of a res, except in the case of God. If this were not the case, a thing (every thing) would not simply be possible in itself, but necesse esse (necessary being) on a par with God. Instead, being seems to be an accident, or rather it has almost the mode of an accident (Quodl. I, q. 9). Nevertheless, it is not an accident in the real sense, since it is not added to something pre-existing, but is rather that by virtue of which a thing exists. In other words, we cannot refer here to the Aristotelian definition of accident (that which has its being in another thing or inheres in a subject), but once again to the broader definition given by Avicenna, according to which anything that belongs to a thing, being external to the intention of its essence, can be called an accident (“Sed intelligendum quod ‘accidens’ accipitur hic largissime, secundum quod iuxta modum loquendi Avicennae ‘accidens’ rei appellatur omne quod convenit ei et est extra intentionem suae essentiae”; Quodl. II, q. 8, ed. Wielockx, p. 48, ll. 21-23). In this sense an accident is anything that is external to the intentio of a res as absolute essence, without ever being really distinct from it. With regard to essence, actual being (that is, ratio suppositi) represents an accident of this type. Being is therefore an intentio that occurs to essence without adding anything real, and so it differs from essence only intentionally.