At an early stage of his gradual transformation he is seen defining the novelist as an exponent, an analyst, a dissector of human life. His work is to be accomplished in strict accordance with science, and the methods of the great scientist, Claude Bernard, are held up to him as examples. This idea of "le Roman Expérimental," as Zola finally called the scientific fiction he expounded, had long haunted him; but when he wished to give it really adequate expression he was momentarily at a loss as to where he might find the most forcible and most modern exposition of scientific principles and methods. It was his friend M. Yves Guyot, a many-sided man, then only a journalist, later a Minister of State, and now eminent as a political economist, who recommended him to study Claude Bernard.[17] On that study Zola based one of the most famous of his essays. Science, which appeals so little to some minds, particularly literary minds of the average calibre, is really the greatest humanitarian agency we possess. The man who experiments, the man who dissects, does not do so for mere pleasure; his aim is the increase and diffusion of knowledge, the benefit of the world, the advantage of his fellow-men. That which is learnt in the laboratory, the workshop, the operating room is put to use in a thousand ways. In physiological and medical science the work may often be very repulsive, yet it reveals the causes of many flaws and ailments, and points to the means of cure. A similar aim became Zola's as he proceeded with his novels. He made it his purpose to inquire into all social sores, all the imperfections and lapses of collective and individual life that seemed to him to require remedying. That everything should be made manifest in order that everything might be healed, such was the motto he adopted. Yet in the first instance he did not preach, he did not denounce, he contented himself with stating the facts; he confined himself to analysis, dissection, and demonstration, and he used the novel as his vehicle, because the novel alone appealed to the great majority of people to whom it was necessary that the facts should be made patent if any remedy were to be applied. [Illustration: Zola's Home at Médan, showing the "Assommoir" & "Nana" Towers.] But the prejudiced, the purblind, and the foolish, the hundreds of so-called critics who had glanced at his novels but had never perused a line of the essays in which he enunciated his principles, responded by accusing him of a degraded partiality for filth, of wallowing in mire, because such was his favourite element. The sensation created by "L'Assommoir" had been great, that which attended the production of "Nana" was perhaps greater.