“I wish to guard the Principle of Vision from certain misconceptions which might arise on a simple statement of it. The principle insists on the artist assuring himself that he distinctly sees what he attempts to represent. What he sees, and how he represents it, depend on other principles. To make even this principle of Vision thoroughly intelligible in its application to all forms of Literature and Art, it must be considered in connection with the two other principles — Sincerity and Beauty, which are involved in all successful works.”

The Philosophical Emperor, a Political Experiment, or, The Progress of a False Position: (1841)
Context: His majesty recollected the celebrated quack doctor, who when asked why his patrons were more numerous than those of regular practitioners, replied, that he was patronised by the fools, who are numerous in every community, while regular physicians are patronised by the wise, who are few. His majesty could not see why the principle was not applicable to politics. He resolved to try it. He would so govern as to be patronised by the numerous class, and leave the desires of the few to be regarded by some future emperor, who should choose to make so unpromising an experiment.

Source: The Limits of Evolution, and Other Essays, Illustrating the Metaphysical Theory of Personal Ideaalism (1905), The Art-Principle as Represented in Poetry, p.182

The Principles of Success in Literature (1865)
Context: An artist produces an effect in virtue of the distinctness with which he sees the objects he represents, seeing them not vaguely as in vanishing apparitions, but steadily, and in their most characteristic relations. To this Vision he adds artistic skill with which to make us see. He may have clear conceptions, yet fail to make them clear to us: in this case he has imagination, but is not an artist. Without clear Vision no skill can avail. Imperfect Vision necessitates imperfect representation; words take the place of ideas.

Dialogues on enlightenment and reason (2013)

Reflections on the Motive Power of Heat (1824)

Reason and Rationality (2009)

Robert Grosseteste and the Origins of Experimental Science 1100-1700 (1953)

Source: The Doctrine of the Mean

Source: Mathematical Thought from Ancient to Modern Times (1972), p. 580
Context: Fermat knew that under reflection light takes the path requiring least time and, convinced that nature does indeed act simply and economically, affirmed in letters of 1657 and 1662 his Principle of Least Time, which states that light always takes the path requiring least time. He had doubted the correctness of the law of refraction of light but when he found in 1661 that he could deduce it from his Principle, he not only resolved his doubts about the law but felt all the more certain that his Principle was correct.... Huygens, who had at first objected to Fermat's Principle, showed that it does hold for the propagation of light in media with variable indices of refraction. Even Newton's first law of motion, which states that the straight line or shortest distance is the natural motion of a body, showed nature's desire to economize. These examples suggested that there might be a more general principle. The search for such a principle was undertaken by Maupertuis.