„Necessary truth is merely the subject-matter of mathematics, not the reward we get for doing mathematics. The object of mathematics is not, and cannot be, mathematical certainty. It is not even mathematical truth, certain or otherwise. It is, and must be, mathematical explanation.“

The Notebooks of Leonardo da Vinci (1883), XIX Philosophical Maxims. Morals. Polemics and Speculations.

Pierre Deligne in: Philip Ball. "Mathematician wins award for shaping algebra: 2013 Abel Prize goes to Belgian Pierre Deligne, who proved a deep conjecture about algebra and geometry." in Nature, 20 March 2013

Les Loix du Mouvement et du Repos, déduites d'un Principe Métaphysique (1746)

Elements de la géométrie de l'infini (1727) as quoted by Amir R. Alexander, Geometrical Landscapes: The Voyages of Discovery and the Transformation of Mathematical Practice (2002) citing Michael S. Mahoney, "Infinitesimals and Transcendent Relations: The Mathematics of Motion in the Late Seventeenth Century" in Reappraisals of the Scientific Revolution, ed. David C. Lindberg, Robert S. Westman (1990)

The Philosophy of Space and Time (1928, tr. 1957)

§ 2.
Linear Associative Algebra (1882)
Contesto: The branches of mathematics are as various as the sciences to which they belong, and each subject of physical enquiry has its appropriate mathematics. In every form of material manifestation, there is a corresponding form of human thought, so that the human mind is as wide in its range of thought as the physical universe in which it thinks.

Footnote: In the future by 'mathematics' will always be meant 'pure mathematics'.
The Foundations of Mathematics (1925)

Space, Time and Gravitation (1920)

Origine: The Character of Physical Law (1965), chapter 2, “The Relation of Mathematics to Physics”
Contesto: Mathematics is not just a language. Mathematics is a language plus reasoning. It's like a language plus logic. Mathematics is a tool for reasoning. It's, in fact, a big collection of the results of some person's careful thought and reasoning. By mathematics, it is possible to connect one statement to another.

Origine: Linear programming and extensions (1963), p. 2

Origine: Adventures of a Mathematician - Third Edition (1991), Chapter 3, Travels Abroad, p. 52

Origine: The mechanization of the world picture, 1961, p. 499

Origine: 19th century, Popular Scientific Lectures [McCormack] (Chicago, 1898), p. 197; On mathematics and counting.

Origine: A Mathematical Theory of Systems Engineering (1967), p. 3.

100 Years of Mathematics: a Personal Viewpoint (1981)

UniMath by Vladimir Voevodsky, Heidelberg Laureate Forum, Sept. 22, 2016, Heidelberg https://www.math.ias.edu/vladimir/sites/math.ias.edu.vladimir/files/2016_09_22_HLF_Heidelberg.pdf p. 3

1900s, "The Study of Mathematics" (November 1907)
Contesto: Mathematics, rightly viewed, possesses not only truth, but supreme beauty – a beauty cold and austere, like that of sculpture, without appeal to any part of our weaker nature, without the gorgeous trappings of painting or music, yet sublimely pure, and capable of a stern perfection such as only the greatest art can show. The true spirit of delight, the exaltation, the sense of being more than Man, which is the touchstone of highest excellence, is to be found in mathematics as surely as in poetry. What is best in mathematics deserves not merely to be learnt as a task, but to be assimilated as a part of daily thought, and brought again and again before the mind with ever-renewed encouragement.

Bk. 1, ch. 4. Translated by Robert B. Burke, in: Edward Grant (1974) Source Book in Medieval Science. Harvard University Press. p. 93
Opus Majus, c. 1267

Digital Typography, ch. 1, p. 8 (1999)