“In the interval of my great philosophical labours,” he writes on the 8th September, 1824, “I propose to publish a few more special works upon the fundamental points in mathematics, which I have long conceived, and which I have at last been able to connect with my general ideas of positive philosophy: so that I shall be free to give myself up to them without _breaking through the unity of my thought_, which is the great condition for the life of a thinker.”[3] And in a very remarkable letter to de Blainville, on the 27th February, 1826, he explains in the clearest way the generating idea of his system. “My conception of politics as social physics, and the law which I have discovered upon the three successive states of the human mind are but one and the same thought, considered from the two distinct points of view of method and of science. That being established, I shall show that this single thought directly and completely satisfies the great actual social need, _considered under its two aspects of theoretical need and practical need_. I will therefore show that what on one hand tends to consolidate the future by re-establishing order and discipline among intellects, tends, on the other hand to regulate the present, as far as possible, by furnishing statesmen with _rational_ lines to work upon.”[4] Henceforth Comte’s life was to be but the methodical execution of his programme. In turn, with perfect regularity, he wrote and published the philosophy of the sciences and of history, the ethics, the positive polity and the positive religion. Does this mean that Comte’s thought remained stationary? Most certainly not. It evolved from 1822 to 1857. But this evolution followed a curve which an attentive observer might have sketched beforehand after having read the _Plan des travaux scientifiques nécéssaires pour réorganiser la société_. Comte had but one system, not two. From the _opuscules_ of his twentieth year to the _Synthèse subjective_ of his last year, it is the development of one and the same conception. III. The unity of the doctrine has been disputed. Comte himself distinguished two successive “careers” in his life. In the first, he says, without affected modesty, he was Aristotle: in the second he will be St. Paul. The founder of the philosophy did but pave the way for the organiser of the religion. “I have systematically devoted my life to draw at last from real science the necessary basis of a sound philosophy, according to which I was afterwards to construct the true religion.”[5] Many of Comte’s disciples, even some of the more illustrious, and at first more fervent, such as Littré, refused to follow him in his “second career.” Their admiration for the philosopher could not persuade them to submit to the pontiff.