Among the features characteristic of the modern mentality the tendency to bring everything down to an exclusively quantitative point of view will be taken from now on as the central theme of this treatise This tendency is most marked in the scientific conceptions recent centuries but it is almost as conspicuous in other domains, notably in that of social organisation; so much so that with one reservation the nature and necessity of which will appear hereafter, our period could almost be defined as being essentially and primarily the "reign of quantity". This characteristic is chosen in preference to any other not solely nor even principally because it is one of the most evident and least contestable but above all because of its truly fundamental nature for reduction to the quantitative is strictly in conformity with the conditions of the cyclic phase at which humanity has now arrived."