“Weight, force and casual impulse, together with resistance, are the four external powers in which all the visible actions of mortals have their being and their end.”
The Notebooks of Leonardo da Vinci (1883), XIX Philosophical Maxims. Morals. Polemics and Speculations.
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Leonardo Da Vinci 363
Italian Renaissance polymath 1452–1519Related quotes

Six Principles of Political Realism, § 5.
Politics Among Nations (1948)
Context: Political realism refuses to identify the moral aspirations of a particular nation with the moral laws that govern the universe. As it distinguishes between truth and opinion, so it distinguishes between truth and idolatry. All nations are tempted — and few have been able to resist the power for long — to clothe their own aspirations and action in the moral purposes of the universe. To know that nations are subject to the moral law is one thing, while to pretend to know with certainty what is good and evil in the relations among nations is quite another. There is a world of difference between the belief that all nations stand under the judgment of God, inscrutable to the human mind, and the blasphemous conviction that God is always on one's side and that what one wills oneself cannot fail to be willed by God also.
“The Phaedrus and the Nature of Rhetoric,” p. 24.
The Ethics of Rhetoric (1953)

Source: The Martyrdom of Man (1872), Chapter IV, "Intellect"

“In established interests are the most powerful force of resistance to good.”
“The power and force of stone reside in its mass, its weight, and its density.”
Source: The Human Form: Sculpture, Prints, and Drawings, 1977, p. 19.

Source: Master of Precision: Henry M. Leland, 1966, p. 147; Leland talking about his idea for a V8 engine around 1913-14. Partly cited in: Alexander Richard Crabb (1969), Birth of a giant: the men and incidents that gave America the motorcar. p. 315