Raban, however, had somewhat larger thoughts of education than his master. For example, he takes a broader view of grammar, which he regards as the _scientia_ of interpreting the poets and historians, and the _ratio_ of correct speech and writing.[260] Likewise he treats _Dialectica_ more seriously. With him it is the “_disciplina_ of rational investigation, of defining and discussing, and distinguishing the true from the false. It is therefore the _disciplina disciplinarum_. It teaches how to teach and how to learn; in this same study, reason itself demonstrates what it is and what it wills. This art alone knows how to know, and is willing and able to make knowers. Reasoning in it, we learn what we are, and whence, and also to know Creator and creature; through it we trace truth and detect falsity, we argue and discover what is consequent and what inconsequent, what is contrary to the nature of things, what is true, what is probable, and what is intrinsically false in disputations. Wherefore the clergy ought to know this noble art, and have its laws in constant meditation, so that subtly they may discern the wiles of heretics, and confute their poisoned sayings with the conclusions of the syllogism.”[261] This somewhat extravagant but not novel view of logic’s function was prophetic of the coming scholastic reliance upon it as the means and instrument of truth. Rabanus had no hesitancy in commending this edged tool to his pupils. But the operations of his mind were predominantly Carolingian, which is to say that ninety-nine per cent of the contents of his _opera_ consist of material extracted from prior writers. His Commentaries upon Scripture outbulk all his other works taken together, and are compiled in this manner. So is his encyclopaedic compilation, _De universo libri XXII._,[262] two books more than those of Isidore’s _Etymologies_, from which he chiefly drew; but he changed the arrangement, and devoted a larger part of his parchment to religious topics; and he added further matter gleaned from the Church Fathers, from whom he had drawn his Commentaries. This further matter consisted of the mystical interpretations of things, which he subjoined to their “natural” explanations. He says, in his Praefatio, addressed to King Louis: “Much is set forth in this work concerning the natures of things and the meanings of words, and also as to the mystical signification of things. Accordingly I have arranged my matter so that the reader may find the historical and mystical explanations of each thing set together--_continuatim positam_; and may be able to satisfy his desire to know both significations.” These allegorical elaborations accorded with the habits of this compiler of allegorical comment upon Scripture.[263]