“For every fact there is an infinity of hypotheses.”

Introduction à l'Étude de la Médecine Expérimentale (1865)

Ben Yamen's Song of Geometry (1853)
Context: The Key! it is of wonderful construction, with its infinity of combination, and its unlimited capacity to fit every lock. … it is the great master-key which unlocks every door of knowledge and without which no discovery which deserves the name — which is law, and not isolated fact — has been or ever can be made. Fascinated by its symmetry the geometer may at times have been too exclusively engrossed with his science, forgetful of its applications; he may have exalted it into his idol and worshipped it; he may have degraded it into his toy... when he should have been hard at work with it, using it for the benefit of mankind and the glory of his Creator.

Source: The Golden Bough (1890), Chapter 5, The Magical Control of the Weather.

Language Education in a Knowledge Context (1980)
Context: Definitions, like questions and metaphors, are instruments for thinking. Their authority rests entirely on their usefulness, not their correctness. We use definitions in order to delineate problems we wish to investigate, or to further interests we wish to promote. In other words, we invent definitions and discard them as suits our purposes. And yet, one gets the impression that... God has provided us with definitions from which we depart at the risk of losing our immortal souls. This is the belief that I have elsewhere called "definition tyranny," which may be defined... as the process of accepting without criticism someone else's definition of a word or a problem or a situation. I can think of no better method of freeing students from this obstruction of the mind than to provide them with alternative definitions of every concept and term with which they must deal in a subject. Whether it be "molecule," "fact," "law," "art," "wealth," "gene," or whatever, it is essential that students understand that definitions are hypotheses, and that embedded in them is a particular philosophical, sociological, or epistemological point of view.

Source: The Four Steps to the Epiphany (2013), p. 83

Source: 1830s, Nature http://www.emersoncentral.com/nature.htm (1836), Ch. 4, Language

Commentarius in VIII Libros Physicorum Aristoteles (c. 1230-1235)

The Phenomenon of Man (1955)

As quoted in A Modern Introduction to Logic (1930), p. 198.