The critical principle demanded an examination, for instance, of the contribution of different periods, thus to some extent embarking on historical linguistics.

Linguistics will have to recognise laws operating universally in language, and in a strictly rational manner, separating general phenomena from those restricted to one branch of languages or another.

It is only since linguistics has become more aware of its object of study, i.e. perceives the whole extent of it, that it is evident that this science can make a contribution to a range of studies that will be of interest to almost anyone.

In fact, from then on scholars engaged in a kind of game of comparing different Indo-European languages with one another, and eventually they could not fail to wonder what exactly these connections showed, and how they should be interpreted in concrete terms.