“It is dangerous when speaking of Diderot to try to characterize his philosophy as a whole at any given time by a certain term and, so to speak, to nail it down in this way. For Diderot’s thought can only be grasped on the wing, that is, in the stages of its unceasing transitions. (…) In the course of his life Diderot changed his viewpoint countless times, but the change in itself is neither accidental nor arbitrary. It is an indication of Diderot’s belief that no particular viewpoint from which we contemplate the universe can do justice to its profusion, its inner variety, its constant mutations. Thus Diderot’s thinking does not strive for crystallization, for expression in definitive formulas. It is and remains a fluid and fleeting element; but it is precisely in this elasticity that Diderot believes he can come nearer to reality, which itself knows no rest but is forever in flux.
This infinitely changeable universe can only be understood by a flexible manner of thinking, by a kind of thinking which permits itself to be borne and driven from one flight to the next, which does not rest content with what is present and given, but which rather luxuriates in the abundance of possibilities and wants to explore and test them. (…) His philosophy is a truly dynamic view of the world. All conceptual schemes, all attempts at mere classification, appear to Diderot as narrow-minded and inadequate; they seem to him useful only to describe the state of knowledge at a particular moment. (…) Our minds must remain open to all new possibilities; we must allow the horizon of experience to be narrowed by any systems or rules. These considerations lead Diderot to a new conception of the philosophy of nature. It is vain to confine nature within limits, vain to seek to subject it to our human classifications. Nature knows only diversity and absolute heterogeneity. None of its forms retains its identity; each form represents merely a transitory state of equilibrium of its shaping forces which can and will cease to be. 
“Just as in the animal and vegetable kingdoms, an individual so to speak begins, develops, endures, perishes and vanishes, might it not be the same with whole species?… Who knows all the animal species which have gone before us? Who knows the species which will follow ours? Everything changes, everything passes away; only the whole is permanent. The world is constantly waxing and waning; it begins and ends at every instant… In the immeasurable ocean of matter, there is no molecule which resembles any other molecule – nay, not even itself – for a single moment. ‘A new order of things is born’: such is the eternal motto of the universe.” 
 CASSIRER, Ernst. The Philosophy of the Enlightenment. Princeton University Press, 1951. Pg. 90-91.
 DIDEROT, Denis. De l’Interprétation de la Nature. Sect. LVIII. In: Oeuvres, ed. Assézat, vol. II, pp. 57.