
P.A.M. Dirac, "Pretty Mathematics," International Journal of Theoretical Physics, Vol. 21, Issue 8–9, August 1982, p. 603 http://link.springer.com/article/10.1007/BF02650229#page-1
The Substitution of Similars, The True Principles of Reasoning (1869)
Context: Aristotle's dictim... may then be formulated somewhat as follows:—Whatever is known of a term may be stated of its equal or equivalent. Or, in other words, Whatever is true of a thing is true of its like.... the value of the formula must be judged by its results;... it not only brings into harmony all the branches of logical doctrine, but... unites them in close analogy to the corresponding parts of mathematical method. All acts of mathematical reasoning may... be considered but as applications of a corresponding axiom of quantity...
P.A.M. Dirac, "Pretty Mathematics," International Journal of Theoretical Physics, Vol. 21, Issue 8–9, August 1982, p. 603 http://link.springer.com/article/10.1007/BF02650229#page-1
Preface (March 30, 1807)
A Course of Lectures on Natural Philosophy and the Mechanical Arts (1807)
Preface
The Substitution of Similars, The True Principles of Reasoning (1869)
“All scientific conclusions are based on axioms, all reasoning depends ultimately upon faith.”
"The Holy Dimension", p. 338
Moral Grandeur and Spiritual Audacity: Essays (1997)
Context: Reality is not exhausted by knowledge. Inaccessible to research are the ultimate facts. All scientific conclusions are based on axioms, all reasoning depends ultimately upon faith. Faith is virgin thinking, preceding all transcendent knowledge. To believe is to abide at the extremities of spirit.
“It is not of the essence of mathematics to be conversant with the ideas of number and quantity.”
Source: 1850s, An Investigation of the Laws of Thought (1854), p. 12; Cited in: Alexander Bain (1870) Logic, p. 191
[Louis Poinsot, translated by Charles Thomas Whitley, Outlines of a new theory of rotatory motion, R. Newby (Cambridge), 1834, 4]
Methods of Mathematics Applied to Calculus, Probability, and Statistics (1985)