The "Esse Similitudinale" of "Species" in Roger Bacon’s "Liber de sensu et sensato"

Roger Bacon’s theory of perception, grounded in his original conception of "species" and of their multiplication and reception, has always been the object of considerable scholarly attention. Yet, modern studies have traditionally focused on Bacon’s mature works. In these works, especially in the "De multiplicatione specierum", Bacon endorses a strong 'materialist' position with respect to the kind of being that "species" have in the medium and in the senses. In this paper I show that an alternative conception of the ontology of "species" is presented by Bacon in his commentary on Aristotle’s "De sensu et sensato". This work is situated at a critical juncture in Bacon’s intellectual journey, since it is the last of his extant Aristotelian commentaries, while it precedes all his mature works. As I will argue in this paper, in these works Bacon assigns to "species" an ‘"esse similitudinale"’, which he explicitly defines as the composition of "esse materiale" and "esse formale". As a result, Bacon did not always deem "species" to be merely composed of "esse materiale". I end by suggesting that this finding might have some implications on the interpretation of Bacon’s mature ontology of species as detailed in the "De multiplicatione specierum".