“In fact the opposition of instinct and reason is mainly illusory. Instinct, intuition, or insight is what first leads to the beliefs which subsequent reason confirms or confutes; but the confirmation, where it is possible, consists, in the last analysis, of agreement with other beliefs no less instinctive. Reason is a harmonising, controlling force rather than a creative one. Even in the most purely logical realms, it is insight that first arrives at what is new.”

Appearance and Reality, preface (1893).

Source: Straight From The Heart (1985), Chapter Three, The Business Of politics, p. 67
Context: A successful politician must not only be able to read the mood of the public, he must have the skill to get the public on his side. The public is moved by mood more than logic, by instinct more than reason, and that is something that every politician must make use of or guard against

Source: The Characteristics of the Present Age (1806), p. 7

Idea for a Universal History from a Cosmopolitan Point of View (1784)
Context: Reason in a creature is a faculty of widening the rules and purposes of the use of all its powers far beyond natural instinct; it acknowledges no limits to its projects. Reason itself does not work instinctively, but requires trial, practice, and instruction in order gradually to progress from one level of insight to another. Therefore a single man would have to live excessively long in order to learn to make full use of all his natural capacities. Since Nature has set only a short period for his life, she needs a perhaps unreckonable series of generations, each of which passes its own enlightenment to its successor in order finally to bring the seeds of enlightenment to that degree of development in our race which is completely suitable to Nature’s purpose. This point of time must be, at least as an ideal, the goal of man’s efforts, for otherwise his natural capacities would have to be counted as for the most part vain and aimless. This would destroy all practical principles, and Nature, whose wisdom must serve as the fundamental principle in judging all her other offspring, would thereby make man alone a contemptible plaything.

Second Thesis
Paraphrased variant: Reason does not work instinctively, but requires trial, practice, and instruction in order to gradually progress from one level of insight to another.

How we love to play with words that please our pride;
Our noble race's mean descent by false forged titles seek to hide! <p> For "gift divine" I bid you read the better work of higher brain,
From Instinct diff'ering in degree as golden mine from leaden vein.
The Kasîdah of Hâjî Abdû El-Yezdî (1870)

Source: The Characteristics of the Present Age (1806), p. 8

quoted by his brother-in-law Claude Terrasse, in 'Introduction' of Pierre Bonnard, John Rewald; MoMA - distribution Simon & Schuster, New York, 1918