“What do you believe was on the mind of the ancient Romans that they called the arts of speaking humanity? They judged that, indisputably, by the study of these disciplines not only was the tongue refined, but also the wildness and barbarity of people’s minds was amended.”

As quoted in "Van Wagenen Fellowship Richard M. Bergland 1968 Oxford University," American Association of Neurological Surgeons (2004)

Les anciens Romains élevaient des prodiges d'architecture pour faire combattre des bêtes.
Letter addressed to "un premier commis" [name unknown] (20 June 1733), from Oeuvres Complètes de Voltaire: Correspondance [Garnier frères, Paris, 1880], vol. I, letter # 343 (p. 354)
Citas

The Evolution of Physics (1938) (co-written with Leopold Infeld) <!-- later published by Simon & Schuster (1967) -->
1930s
Context: Physical concepts are free creations of the human mind, and are not, however it may seem, uniquely determined by the external world. In our endeavor to understand reality we are somewhat like a man trying to understand the mechanism of a closed watch. He sees the face and the moving hands, even hears its ticking, but he has no way of opening the case. If he is ingenious he may form some picture of a mechanism which could be responsible for all the things he observes, but he may never be quite sure his picture is the only one which could explain his observations. He will never be able to compare his picture with the real mechanism and he cannot even imagine the possibility or the meaning of such a comparison. But he certainly believes that, as his knowledge increases, his picture of reality will become simpler and simpler and will explain a wider and wider range of his sensuous impressions. He may also believe in the existence of the ideal limit of knowledge and that it is approached by the human mind. He may call this ideal limit the objective truth.

Source: 11/22/63 (2011), Chapter Final Notes, page 1030,(First Scribner hardcover edition November 2011)
Source: https://web.archive.org/web/20210722191755/https://libquotes.com/stephen-king/quote/lbj3k9y Archived] from [https://libquotes.com/stephen-king/quote/lbj3k9y the original

The Notebooks of Leonardo da Vinci (1883), XIX Philosophical Maxims. Morals. Polemics and Speculations.
Context: Every action needs to be prompted by a motive. To know and to will are two operations of the human mind. Discerning, judging, deliberating are acts of the human mind.

Mos antiquis fuit, usque ad meam servatus aetatem, primis epistulae verbis adicere 'si vales bene est, ego valeo'. Recte nos dicimus 'si philosopharis, bene est'.
Valere enim hoc demum est. Sine hoc aeger est animus.
Epistulae Morales ad Lucilium (Moral Letters to Lucilius), Letter XV

Source: The Complete Essays