 The first main part of the Tractatus divides into five tracts. The first tract, De introductionibus (On introductory topics) explains the concepts used in traditional logic—nomen (noun), verbum (verb), oratio (phrase), propositio (proposition)—and presents the divisions of and the (logical) relationships between propositions. The second tract, De predicabilibus (On the predicables) covers matters dealt with in Boethius’s accounts of Porphyry’s Isagoge. It gives an account of the concept predicabile and the five predicables—genus, species, differentia, proprium, accidens—i.e., the common features of and differences between the predicables, as well as of the terms ‘predicatio’ and ‘denominativum’. Tract three, De predicamentis (On the categories), discusses the ten Aristotelian categories, as well as some items already dealt with in the previous treatise. The fourth tract, De sillogismis (On syllogisms) mainly goes back to Boethius’s De syllogismis categoricis (On categorical syllogisms). It gives an explanation of the basic element of the syllogism, i.e., propositio, and of the syllogism, and then goes into mood and figure, the proper forms of syllogisms, and briefly deals with what are called paralogisms. The fifth tract, De locis (On topical relationships), is derived from Boethius’s De topicis differentiis (On different topical relationships) I and II. This tract starts off with an explanation of the notions argumentum and argumentatio, and then proceeds to deal with the species of argumentation: syllogism, induction, enthymeme, and example. Next, it gives a definition of locus (the Latin translation of the Greek topos): a locus is the seat of an argument (i.e., the locus is supposed to warrant the inference by bringing it under some generic rule.) The intrinsic loci (= the kind of locus that occurs when the argument is derived from the substance of the thing involved) are covered first, followed by the extrinsic loci (= the kind of locus that occurs when the argument is derived from something that is completely separate from the substance of the thing involved) and intermediary loci (= the kind of locus that occurs when the argument is taken from the things that partly share in the terms of the problem and partly differ from it). Examples are: intrinsic—the locus “from definition”: ‘a rational animal is running; therefore a man is running’; extrinsic—the locus “from opposites”: ‘Socrates is black; therefore he is not white’; intermediary—‘the just is good; therefore justice is good’.