the divinity of whom they declare themselves a priori the organs, and while they assume to impose them, even by force, as the eternal rules of private and social life, men of science, having recognized the relative and historical source of these assertions, limit themselves to applying actual rules to the practical conduct of life, in morals and politics as well as in hygiene and industry—rules always provisional, and subject to modification from day to day by the evolution of future ages, as they have been constantly modified in past ages.
The prime characteristic of modern science is its readiness to declare the increasing uncertainty of its ideal constructions. While it does not refuse to examine problems of origin, while it itself furnishes the only probable data by the aid of which the solution of them can be pursued, it affirms nothing and promises nothing in the matter. It would consider it equally rash to set up on similar constructions the rules of industrial applications and moral rules for the conduct of individuals and societies. In real things we never proceed in the name of absolute principles, because we have learned that all our principles rest upon hypotheses borrowed from the facts of observation under a direct or simulated form. To deduce everything from absolute principles is an illusion. Whatever pretends to be supported on the absolute is supported on nothing.
Man's knowledge is gained solely by the method of the observation of facts, but is derived from two sources, an internal and an external one. Sensation reveals the external world to us, and is the point of departure of all the physical, natural, and historical sciences. It exhibits the insignificance and subordination of the individual in mankind, present and past; the insignificance and subordination of mankind overwhelmed and almost reduced to nothing in the infinite whole of the universe. From this point of view, all morals consist in our humble submission to the necessary laws of the world; religions say nothing more than this when they subordinate the human mind to the divine will. In this domain everything is objective.
In the inner world, that of consciousness, on the contrary, the man appears alone; his mind, his feelings, become the measure of things. These have no existence for us, except on the condition that they are known, and therefore from that point of view they exist only for our intelligence and in our intelligence. In this domain all is subjective. Such is the contrast—I do not say opposition—between the two sources of our knowledge. Now, these two sources, internal and external, of our positive knowledge are equally, I repeat, the two sources of our morals.
Human morality, no more than science, does not recognize a divine origin; it does not proceed from religions. Its rules are drawn from