In my _System of Positive Philosophy_ both these objects were aimed at. I attempted, and in the opinion of the principal thinkers of our time successfully, to complete and at the same time co-ordinate Natural Philosophy, by establishing the general law of human development, social as well as intellectual. I shall not now enter into the discussion of this law, since its truth is no longer contested. Fuller consideration of it is reserved for the third volume of my new treatise. It lays down, as is generally known, that our speculations upon all subjects whatsoever, pass necessarily through three successive stages: a Theological stage, in which free play is given to spontaneous fictions admitting of no proof; the Metaphysical stage, characterized by the prevalence of personified abstractions or entities; lastly, the Positive stage, based upon an exact view of the real facts of the case. The first, though purely provisional, is invariably the point from which we start; the third is the only permanent or normal state; the second has but a modifying or rather a solvent influence, which qualifies it for regulating the transition from the first stage to the third. We begin with theological Imagination, thence we pass through metaphysical Discussion, and we end at last with positive Demonstration. Thus by means of this one general law we are enabled to take a comprehensive and simultaneous view of the past, present, and future of Humanity. In my _System of Positive Philosophy_, this law of Filiation has always been associated with the law of Classification, the application of which to Social Dynamics furnishes the second element requisite for the theory of development. It fixes the order in which our different conceptions pass through each of these phases. That order, as is generally known, is determined by the decreasing generality, or what comes to the same thing, by the increasing complexity of the phenomena; the more complex being naturally dependent upon those that are more simple and less special. Arranging the sciences according to this mutual relation, we find them grouped naturally in six primary divisions[2]; Mathematics, Astronomy, Physics, Chemistry, Biology, and Sociology. Each passes through the three phases of developments before the one succeeding it. Without continuous reference to this classification the theory of development would be confused and vague.