Three principles — the conformability of nature to herself, the **applicability** of the criterion of simplicity, and the "unreasonable effectiveness" of certain parts of mathematics in describing physical reality — are thus consequences of the underlying law of the elementary particles and their interactions. Those three principles need not be assumed as separate metaphysical postulates. Instead, they are emergent properties of the fundamental laws of physics.

— TED talk on beauty and truth in physics —video timecode 14m28s (March 2007)

Our assent to the hypothesis implies that it is held to be true of all particular instances. That these cases belong to past or to future times, that they have or have not already occurred, makes no difference in the **applicability** of the rule to them. Because the rule prevails, it includes all cases.

— Part 2, Book 11, ch. 5, sect. 3, art. 10

For a parallel to the lesson of atomic theory regarding the limited **applicability** of such customary idealizations, we must in fact turn to quite other branches of science, such as psychology , or even to that kind of epistemological problems with which already thinkers like Buddha and Lao Tzu have been confronted, when trying to harmonize our position as spectators and actors in the great drama of existence.

— Speech on quantum theory at

For any truth, if overdone (as Dietzgen Senior put it), if exaggerated, or if carried beyond the limits of its **applicability**, can be reduced to absurdity.

—

A theory is the more impressive the greater the simplicity of its premises, the more different kinds of things it relates, and the more extended its area of **applicability**. Therefore the deep impression that classical thermodynamics made upon me. It is the only physical theory of universal content which I am convinced will never be overthrown, within the framework of **applicability** of its basic concepts.

— Albert Einstein (author), Paul Arthur, Schilpp (editor). Autobiographical Notes. A Centennial Edition. Open Court Publishing Company. 1979. p. 31 [As quoted by Don Howard, John Stachel. Einstein: The Formative Years, 1879-1909 (Einstein Studies, vol. 8). Birkhäuser Boston. 2000. p. 1]

It appears to me to be the duty of every Court, whether a Court of equity or a Court of law, to give effect to the plain meaning of the Legislature, whatever may be the views entertained of its policy or **applicability** in particular cases.

— Sir W. M. James, V.-C,

* Three principles the conformability of nature to herself, the **applicability** of the criterion of simplicity, and the "unreasonable effectiveness" of certain parts of mathematics in describing physical reality are thus consequences of the underlying law of the elementary particles and their interactions.

— Murray Gell-Mann

Trying to solve real-world problems, researchers often discover that the tools they need were developed years, decades or even centuries earlier by mathematicians with no prospect of, or care for, **applicability**.

— Peter Rowlett, "The unplanned impact of mathematics",