It is not my intention, nor is it necessary for my present purpose, to offer any remarks on the strictly scientific portion of his voluminous work. I shall confine myself exclusively to those speculations which bear, more or less directly, on the great cause of Natural and Revealed Religion, selecting them from all the various parts of his work, and exhibiting them, in one comprehensive view, as a compact theory of absolute and avowed Atheism. The fundamental idea of his system is a supposed "law of the development of human thought," which regulates and determines the whole progress of the species in the acquisition of knowledge. This law is announced with the air of a man who has made a great discovery, and who is entitled, in consequence, to be regarded both as an original thinker, and as a benefactor to the world. "I believe," he says, "that I have discovered a grand fundamental law,"--"the fundamental law of the development of the human mind;" ... "the grand law which I have indicated in the first part of my system of Positive Politics, ... where I have divulged, for the first time, the discovery of this law."[57] Now, what, it may be asked, is this marvellous discovery, which bids so fair both to immortalize its author and to enlighten the world? It is stated briefly in the _first_, and illustrated at greater length in the _fourth_ and following volumes of his work. The general outline of his theory is thus sketched: "That law consists in this,--that each one of our leading conceptions, every branch of our knowledge, passes successively through _three different theoretic states_: the state theological or fictitious, the state metaphysical or abstract, and the state scientific or positive. In other words, the human mind, by its nature, employs successively, in each of its researches, three methods of philosophizing, whose character is essentially different, and even _radically opposed_: first, the Theological method; then, the Metaphysical; and, last of all, the Positive. Hence three systems of Philosophies, which _mutually exclude each other_. The first is the necessary starting-point of the human mind; the third is its fixed, ultimate state; the second is purely provisional, and destined merely to serve as an intermediate stage."[58] These are the _three_ great stages through which the collective mind of Humanity must necessarily pass in its progressive advancement towards a perfect knowledge of truth; but of these three, the _first_, or the Theological Epoch, is again subdivided, and exhibited as commencing with Fetishism, then advancing to Polytheism, and finally consummated in Monotheism.