IRÈNE ROSIER: Roger Bacon and the ellipsis of the subject. The speculative grammar of the Modists, which appears around the middle of the XIIth century, rejects the study of rhetorical figures and focuses on the forms of simple and canonical discourse. On the other hand, although Roger Bacon, one of the major figures of the century, is one of the immediate grammatical forerunners of the Modists, his Summa grammatica only deals with figures. This point of view, however, does not keep him from engaging in the quest for basic rules: since each figure raises a double question -what is the «vice» and what is the «ratio excusans» a rule must first be set up in order to show subsequently how it may have been violated. This paper deals mainly with the problem of the ellipsis of the subject, a point which is at the crossroads of logic and grammar and which is treated differently by the two disciplines. The questions are: is cu" it a complete sentence, is there a type of semantic completeness distinct from morpho-syntactic completeness, is it the nominative form of the noun, or the pronoun, which is understood, what distinguishes the currit structure from ille cu" it, what kinds of words can or should be reconstructed when the subject is not explicit, etc. This leads to a discussion of the notion of «supposition», an ambiguous term which denotes both a word, with the function of grammatical subject, and an object, that is to say what a noun refers to.