"The central idea of the consilience world view is that all tangible phenomena, from the birth of stars to the workings of social institutions, are based on material processes that are ultimately reducible, however long and tortuous the sequences, to the laws of physics. In support of this idea is the conclusion of biologists that humanity is kin to all other life forms by common descent. We share essentially the same DNA genetic code, which is transcribed in to RNA and translated into proteins with the same amino acids. Our anatomy places us among the Old World monkeys and apes. The fossil record shows our immediate ancestor to be either Homo ergaster or Homo erectus. It suggests that the point of our origin was Africa about two hundred thousand years ago. Our hereditary human nature, which evolved during hundreds of millennia before and afterward, still profoundly affects the evolution of culture. (Consilience 266-67).
In Le roman expérimental, Zola proposes to introduce in literature the experimental method of science as defined by the medical scientist Claude Bernard in his Introduction à l'étude de la médecine expérimentale. Zola believes that in this way he will give to his literary theory "the rigidity of a scientific truth" (In Adams, Critical Theory since Plato 647). All sciences can be reduced to the same principles, he believes: it is only a question of degree which separates chemistry from sociology. All bodies, living or inanimate, are determined, all follow inflexible laws of behaviour. Man is not an exception. The purpose of the experimental novel will be to demonstrate these laws. Like all scientific procedures, the experimental novel only shows the "how" of the process, not the "why." Asking for causes is not a scientific question, Zola affirms. The novelist looks for laws, not for the cause of the laws.
Although Zola set a heavy emphasis on documentation, watching factories and shops, little notebooks, etc., this search for laws is not done through mere observation, but through experiment. An experiment is a modification of nature without departing from it (cf. symbol). The novelist is both an observer and an experimentalist; he forms a hypothesis by observing some facts in real life, and then checks it by writing a novel. He places characters in a situation appropriate to the testing of that experience. The hypothesis must be confirmed by the result of the situation, without a violation of the laws of nature. Zola seriously believes that this is a scientific approach to literature: "It is undeniable that the naturalistic novel, such as we understand it today, is a real experiment that a novelist makes on man by the help of observation" (Zola 649)
He acknowledges however that the task is difficult, that the experimental novel is just born and that it cannot yet give any fixed laws of human behaviour: heredity and surrounding, however, are obviously very important. But in time, he says, the experimental novel will help psychology become an exact science: "A like determinism will govern the stones of the roadway and the brain of man" (Zola 650). This knowledge will be used in the future "to be masters of good and evil, to regulate life, to regulate society, to solve in time all the problems of socialism" (652).
Hyppolite Taine's positivism, which inspired Zola, is also on the same wavelength. For Taine, art, philosophy and religion all spring from the same principle: the conception of the world of a specific people. The art of a people is its philosophy made sensible. Literature, in particular, is the best document available to us for the study of the past. It is more determined than religion or philosophy; it reveals us with great clarity the world conception of an age through the world conception of some of its most perceptive representatives; it leads us to social psychology through individual psychology. "In this light, a great poem, a fine novel, the confession of a superior man, are more instructive than a heap of historians with their histories" (Introduction to History of English Literature, in Adams, Critical Theory since Plato 613). This is not to be interpreted as a statement of the superiority of literature over history. Literature is studied only as a historical document. Taine is opposing the external history written in the past, and wants to develop something like a cultural history. All writings, good or bad, are significant, and all must be studied. The best literary works are for Taine the most revealing documents; "their utility grows with their perfection" (614). But in the last analysis the aim of the study of literature is not aesthetic: like the rest of Taine's historical work, it tries to draw a bridge between physical sciences and cultural phenomena in the somewhat reductive fashion of nineteenth-century scientism: "It is then chiefly by the study of literature that one may construct a moral history, and advance towards the knowledge of physical laws from which events spring" (614).
Positivism was the nineteenth century's version of consilience, a bridge perhaps neglected by Wilson in the transition from the Enligtenment to his own intellectual tradition. And a significant step in this tradition might be Herbert Spencer, the great English spokesman for positivism and evolution, and the propounder of a global theory of cosmic evolution linking the origin of the cosmos to the the principles of human activity, within a single coherent explanation based on the laws of physics as he conceived them.