  Henry here introduces his well-known distinction between res a reor reris and res a ratitudine (cf. above all Summa, art. 21, q. 4; art. 24, q. 3; Porro 2011). In the first case, a thing is considered in its purely nominal conception, to which a reality, outside a purely mental one, need not correspond (reor is here synonymous with opinor — to imagine, to suppose). As such, a res a reor reris is in itself indifferent to both being (essentiae and existentiae) and non-being: to cite the most common example, a res a reor reris can be a mythical animal such as a hircocervus or tragelaphus (goat-stag). In the second case, a thing is “certified” (rata) by the fact that it possesses at least the being of an essence. If the nothing that stands in opposition to a res a reor reris cannot even be conceived, the nothing that stands in opposition to a res a ratitudine is not the lack of actual being, hence non-existence in the physical world, but rather the lack of formal constitution: the fact that a thing can be conceived (for example, a chimera or a mountain of gold) without in reality being “certified” as a determined essence. But whence does the being of an essence come? Every essence is what it is in reason of its nature (“Est autem id quod est essentia in unaquaque re communiter loquendo id quod ei convenit ratione naturae suae secundum se.”; Quodl. X, q. 8, ed. Macken, p. 201, ll. 85-87). A stone is a stone because of its own nature, and the same is true for a triangle. Formally, every essence is therefore what it is, in and of itself, albeit through participation (participative), since the very fact of being an essence, content aside, is dependent on God.