“In studying the entire development of the human intelligence in its different spheres of activity, from its first efforts the most simple up to our own days, I believe I have discovered a great fundamental law, to which it is subjected by an invariable necessity, and which seems to me capable of being firmly established, whether on those proofs which are furnished by a knowledge of our organization, or on those historical verifications which result from an attentive examination of the past.  The law consists in this—­that each of our principal conceptions, each branch of our knowledge, passes successively through three different states of theory:  the theologic, or fictitious; the metaphysic, or abstract; the scientific, or positive.  In other terms, the human mind, by its nature, employs successively, in each of its researches, three methods of philosophizing, the character of which is essentially different, and even radically opposed; at first the theologic method, then the metaphysical, and last the positive method.  Hence three distinct philosophies, or general systems of conceptions on the aggregate of phenomena, which mutually exclude each other; the first is the necessary starting-point of the human intelligence; the third is its fixed and definite state; the second is destined to serve the purpose only of transition.

“In the theologic state, the human mind, directing its researches to the intimate nature of things, the first causes and the final causes of all those effects which arrest its attention, in a word, towards an absolute knowledge of things, represents to itself the phenomena as produced by the direct and continuous action of supernatural agents, more or less numerous, whose arbitrary intervention explains all the apparent anomalies of the universe.

“In the metaphysic state, which is, in its essence, a modification of the former, the supernatural agents are displaced by abstract forces, veritable entities (personified abstractions) inherent in things, and conceived as capable of engendering by themselves all the observed phenomena—­whose explanation, thenceforth, consists in assigning to each its corresponding entity.

“At last, in the positive state the human mind, recognizing the impossibility of obtaining absolute notions, renounces the search after the origin and destination of the universe, and the knowledge of the intimate causes of phenomena, to attach itself exclusively to the discovery, by the combined efforts of ratiocination and observation, of their effective laws; that is to say, their invariable relations of succession and of similitude.  The explanation of things, reduced now to its real terms, becomes nothing more than the connexion established between the various individual phenomena and certain general facts, the number of which the progress of science tends continually to diminish.