This is embodied in the group of treatises later known as the _Organon_[28] and culminates in the theory of syllogism and of demonstrative knowledge in the _Analytics_. All else is finally subsidiary. In the well-known sentences with which the _Organon_ closes[29] Aristotle has been supposed to lay claim to the discovery of the principle of syllogism. He at least claims to have been the first to dissect the procedure of the debate-game, and the larger claim may be thought to follow. In the course of inquiry into the formal consequences from probable premises, the principle of mediation or linking was so laid bare that the advance to the analytic determination of the species and varieties of syllogism was natural. Once embarked upon such an analysis, where valid process from assured principles gave truth, Aristotle could find little difficulty in determining the formula of demonstrative knowledge or science. It must be grounded in principles of assured certainty and must demonstrate its conclusions with the use of such middle or linking terms only as it is possible to equate with the real ground or cause in the object of knowledge. Hence the account of axioms and of definitions, both of substances and of derivative attributes. Hence the importance of determining how first principles are established. It is, then, a fair working hypothesis as to the structure of the _Organon_ to place the _Topics_, which deal with dialectical reasoning, before the _Analytics_.[30] Of the remaining treatises nothing of fundamental import depends on their order. One, however, the _Categories_, may be regarded with an ancient commentator,[31] as preliminary to the dialectical inquiry in the _Topics_. The other, on thought as expressed in language ([Greek: Peri ermêneias]) is possibly spurious, though in any case a compilation of the Aristotelian school. If genuine, its naïve theory that thought copies things and other features of its contents would tend to place it among the earliest works of the philosopher. The logical treatises.