The second stage， a return to nature. - Diderot， d'Holbach and the materialists. - Theory of animated matter and spontaneous organization. - The moral of animal instinct and self-interest properly understood.
Here begins the second philosophic expedition. It consists of two armies： the first composed of the encyclopedists， some of them skeptics like d'Alembert， others pantheists like Diderot and Lamarck， the second open atheists and materialists like d'Holbach， Lamettrie and Helvétius， and later Condorcet， Lalande and Volney， all different and independent of each other， but unanimous in regarding tradition as the common enemy. As a result of prolonged hostilities the parties become increasingly exasperated and feel a desire to be master of everything， to push the adversary to the wall， to drive him out of all his positions. They refuse to admit that Reason and tradition can occupy and defend the same citadel together； as soon as one enters the other must depart； henceforth one prejudice is established against another prejudice. -- In fact， Voltaire， "the patriarch， does not desire to abandon his redeeming and avenging God；"[13] let us tolerate in him this remnant of superstition on account of his great services；let us nevertheless examine this phantom in man which he regards with infantile vision. We admit it into our minds through faith， and faith is always suspicious. It is forged by ignorance， fear， and imagination， which are all deceptive powers. At first it was simply the fetish of savages； in vain have we striven to purify and aggrandize it； its origin is always apparent； its history is that of a hereditary dream which， arising in a rude and doting brain， prolongs itself from generation to generation， and still lasts in the healthy and cultivated brain. Voltaire wanted that this dream should be true because， otherwise， he could not explain the admirable order of the world. Since a watch suggests a watchmaker he had firstly to prove that the world is a watch and， then see if the half-finished arrangement， such as it is and which we have observed， could not better be explained by a simpler theory， more in conformity with experience， that of eternal matter in which motion is eternal. Mobile and active particles， of which the different kinds are in different states of equilibrium， these are minerals， inorganic substances， marble， lime， air， water and coal.[14] I form humus out of this， "Isow peas， beans and cabbages；" plants find their nourishment in the humus， and "I find my nourishment in the plants." At every meal， within me， and through me， inanimate matter becomes animate； "Iconvert it into flesh. I animalize it. I render it sensitive." It harbors latent， imperfect sensibility rendered perfect and made manifest. Organization is the cause， and life and sensation are the effects； I need no spiritual monad to account for effects since I am in possession of the cause. "Look at this egg， with which all schools of theology and all the temples of the earth can be overthrown. What is this egg？ An inanimate mass previous to the introduction of the germ. And what is it after the introduction of the germ？ An insensible mass， an inert fluid." Add heat to it， keep it in an oven， and let the operation continue of itself， and we have a chicken， that is to say， "sensibility， life， memory， conscience， passions and thought." That which you call soul is the nervous center in which all sensitive chords concentrate. Their vibrations produce sensations； a quickened or reviving sensation is memory； our ideas are the result of sensations， memory and signs. Matter， accordingly， is not the work of an intelligence， but matter， through its own arrangement， produces intelligence. Let us fix intelligence where it is， in the organized body； we must not detach it from its support to perch it in the sky on an imaginary throne. This disproportionate conception， once introduced into our minds， ends in perverting the natural play of our sentiments， and， like a monstrous parasite， abstracts for itself all our substance.[15] The first interest of a sane person is to get rid of it， to discard every superstition， every "fear of invisible powers."[16] -- Then only can he establish a moral order of things and distinguish "the natural law." The sky consisting of empty space， we have no need to seek commands from on high. Let us look down to the ground； let us consider man in himself， as he appears in the eyes of the naturalist， namely， an organized body， a sensitive animal possessing wants， appetites and instincts. Not only are these indestructible but they are legitimate. Let us throw open the prison in which prejudice confines them； let us give them free air and space；let them be displayed in all their strength and all will go well.
According to Diderot，[17] a lasting marriage is an abuse， being "the tyranny of a man who has converted the possession of a woman into property." Purity is an invention and conventional， like a dress；[18]