This remark has some interest of itself already; but here is what gives it its real importance.
The general conclusion of the book which the reader has before him is that religion is something eminently social. Religious representations are collective representations which express collective realities; the rites are a manner of acting which take rise in the midst of the assembled groups and which are destined to excite, maintain or recreate certain mental states in these groups. So if the categories are of religious origin, they ought to participate in this nature common to all religious facts; they too should be social affairs and the product of collective thought. At least--for in the actual condition of our knowledge of these matters, one should be careful to avoid all radical and exclusive statements--it is allowable to suppose that they are rich in social elements.
Even at present, these can be imperfectly seen in some of them. For example, try to represent what the notion of time would be without the processes by which we divide it, measure it or express it with objective signs, a time which is not a succession of years, months, weeks, days and hours! This is something nearly unthinkable. We cannot conceive of time, except on condition of distinguishing its different moments. Now what is the origin of this differentiation? Undoubtedly, the states of consciousness which we have already experienced can be reproduced in us in the same order in which they passed in the first place; thus portions of our past become present again, though being clearly distinguished from the present. But howsoever important this distinction may be for our private experience, it is far from being enough to constitute the notion or category of time. This does not consist merely in a commemoration, either partial or integral, of our past life. It is an abstract and impersonal frame which surrounds, not only our individual existence, but that of all humanity. It is like an endless chart, where all duration is spread out before the mind, and upon which all possible events can be located in relation to fixed and determined guide lines. It is not _my time_ that is thus arranged; it is time in general, such as it is objectively thought of by everybody in a single civilization. That alone is enough to give us a hint that such an arrangement ought to be collective. And in reality, observation proves that these indispensable guide lines, in relation to which all things are temporally located, are taken from social life. The divisions into days, weeks, months, years, etc., correspond to the periodical recurrence of rites, feasts, and public ceremonies.[5] A calendar expresses the rhythm of the collective activities, while at the same time its function is to assure their regularity.[6]