Thus in mediaeval education, and in the successive order of appropriating the patristic and the antique, logic stood on grammar’s shoulders. It was grammar’s rationalized stage, and treated language as the means of expressing thought consistently and validly; that is, so as not to contravene the necessities of that whereof it was the vehicle. And since language thus treated was in accord with rational thought, it would accord with the realities to which thought corresponds; and might be taken as expressing _them_. This last reflection introduces metaphysics. And properly. For the three stages in the mediaeval appropriation and expression of knowledge were grammar, logic, metaphysics. Logic has to do with the processes of thought; with the positing of premises and the drawing of the conclusion. It does not necessarily consider whether the contents of its premises represent realities. This is matter for ontology, metaphysics. Now mediaeval metaphysics, which were those of Greek philosophy, were extremely pre-Kantian, in assuming a correspondence between the necessities or conclusions of thought and the supreme realities, God and the Universe. Nor did mediaeval logic doubt that its processes could elucidate and express the veritable natures of things. So mediaeval logic readily wandered into the province of metaphysics, and ignored the line between the two. Yet there is little metaphysics in the _Organon_; none in its simpler treatises. So there was none in the elementary logical instruction of the schools before the twelfth century at least.[456] One may always distinguish between logic and metaphysics; and it is to our purpose to do so here. For as we have taken logic to represent the second stage in the mediaeval appropriation of knowledge, so metaphysics, poised in turn on logic’s shoulders, is very representative of the third stage, to wit, the stage of systematic and organic re-expression of the ancient matter, with elements added by the great schoolmen. Metaphysics was very properly the final stage. The grammatical represented an elementary learning of what the past had transmitted; the logical a further retrying of the matter, an attempt to understand and express it, formulate parts of it anew, with deeper consistency of expression. Then follows the attempt for final and universal consistency: final inasmuch as thought penetrates to the nature of things and expresses realities and the relationships of realities; and universal, in that it seeks to order and systematize all its concepts, and bring them to unity in a _Summa_--a perfected scheme of rational presentation of God and His creation. This will be, largely speaking, the final endeavour of the mediaeval man to ease his mind, and realize _his_ impulse to know and express himself with uttermost consistency.