The idea, fundamental both for Bacon and Ps.-Kilwardby, that grammar is a regular science rather than a propaedeutic art, is shared by the school of the so-called “modist grammarians” (modistae) emerging around 1270 in the Faculty of Arts of the University of Paris and culminating in the Grammatica Speculativa of Thomas of Erfurt around 1300. The members of this school, taking it for granted that the objective of any regular science was to explain the facts by giving reasons for them rather than to simply describe them, make it their business to deduce the grammatical features common to all languages from universal modes of being by means of corresponding modes of understanding. Thus the tradition of speculative grammar (grammatica speculativa) develops the commonly accepted Aristotelian claim (De Interpretatione 1.16a3–9) that the mental concepts, just as the things, are the same for all men (eadem apud omnes) further to the thesis of a universal grammar based on the structural analogy between the “modes of being” (modi essendi), the “modes of understanding” (modi intelligendi), and the “modes of signifying” (modi significandi) that are the same for all languages. Along this line, Boethius Dacus (Boethius the Dane), one of the most important theoreticians of speculative grammar,[36] states that … all national languages are grammatically identical. The reason for this is that the whole grammar is borrowed from the things … and just as the natures of things are similar for those who speak different languages, so are the modes of being and the modes of understanding; and consequently the modes of signifying are similar, whence, so are the modes of grammatical construction or speech. And therefore the whole grammar which is in one language is similar to the one which is in another language.[37] Even though the words are arbitrarily imposed (whence arise the differences between all languages), the modes of signifying are uniformly related to the modes of being by means of the modes of understanding (whence arise the grammatical similarities among all languages).