“But the most remarkable thing about prehistoric naturalism is not that it is older than the geometric style, which makes so much more of a primitive impression, but that it already reveals all the typical phases of development through which art has passed in modern times and is not in any sense the merely instinctive, static, a-historical phenomenon which scholars obsessed with geometric and rigorously formal art declare it to be. This is an art which advances from a linear faithfulness to nature, in which individual forms are still shaped somewhat rigidly and laboriously, to a more nimble and sparkling, almost impressionistic technique.”

On poetry

Book II, Ch. I, pp. 93-94.
Physics

Preface, p. 7-8
1910s, Art, 1912

Les passions sont les seuls orateurs qui persuadent toujours. Elles sont comme un art de la nature dont les règles sont infaillibles; et l'homme le plus simple qui a de la passion persuade mieux que le plus éloquent qui n'en a point.
Variant translation: The passions are the only orators who always persuade. They are like a natural art, of which the rules are unfailing; and the simplest man who has passion will be more persuasive than the most eloquent man who has none.
Maxim 8.
Reflections; or Sentences and Moral Maxims (1665–1678)

Source: 1960-70's, Prospectus et tous écrits suivants, 1967, p. 206

Translations, From the French

Origins Reconsidered: In Search of What Makes Us Human (1992)

Christian Mysticism (1899), Preface
Context: The phase of thought or feeling which we call Mysticism has its origin in that which is the raw material of all religion, and perhaps of all philosophy and art as well, namely, that dim consciousness of the beyond, which is part of our nature as human beings. Men have given different names to these "obstinate questionings of sense and outward things." We may call them, if we will, a sort of higher instinct, perhaps an anticipation of the evolutionary process; or an extension of the frontier of consciousness; or, in religious language, the voice of God speaking to us. Mysticism arises when we try to bring this higher consciousness into relation with the other contents of our minds.

L'art est une démonstration dont la nature est la preuve.
François le Champi, Introduction (1848); Jane Minot Sedgwick (trans.) François the Waif {New York: H. M. Caldwell, 1894) p. 17