Thinking consists in arranging our ideas, and consequently in classifying them. To think of fire, for example, is to put it into a certain category of things, in such a way as to be able to say that it is this or that, or this and not that. But classifying is also naming, for a general idea has no existence and reality except in and by the word which expresses it and which alone makes its individuality. Thus the language of a people always has an influence upon the manner in which new things, recently learned, are classified in the mind and are subsequently thought of; these new things are thus forced to adapt themselves to pre-existing forms. For this reason, the language which men spoke when they undertook to construct an elaborated representation of the universe marked the system of ideas which was then born with an indelible trace. Nor are we without some knowledge of this language, at least in so far as the Indo-European peoples are concerned. Howsoever distant it may be from us, souvenirs of it remain in our actual languages which permit us to imagine what it was: these are the roots. These stems, from which are derived all the words which we employ and which are found at the basis of all the Indo-European languages, are regarded by Max Müller as so many echoes of the language which the corresponding peoples spoke before their separation, that is to say, at the very moment when this religion of nature, which is to be explained, was being formed. Now these roots present two remarkable characteristics, which, it is true, have as yet been observed only in this particular group of languages, but which our author believes to be present equally in the other linguistic families.[152] In the first place, the roots are general; that is to say that they do not express particular things and individuals, but types, and even types of an extreme generality. They represent the most general themes of thought; one finds there, as though fixed and crystallized, those fundamental categories of the intellect which at every moment in history dominate the entire mental life, the arrangement of which philosophers have many times attempted to reconstruct.[153] Secondly, the types to which they correspond are types of action, and not of objects. They translate the most general manners of acting which are to be observed among living beings and especially among men; they are such actions as striking, pushing, rubbing, lying down, getting up, pressing, mounting, descending, walking, etc. In other words, men generalized and named their principal ways of acting before generalizing and naming the phenomena of nature.[154]