There never comes a point where a theory can be said to be true. The most that one can claim for any theory is that it has shared the successes of all its rivals and that it has passed at least one test which they have failed.
~ Sir Alfred Jules Ayer

Theories are always very thin and insubstantial, experience only is tangible.
~ Hosea Ballou

It is not enough for theory to describe and analyze, it must itself be an event in the universe it describes. In order to do this theory must partake of and become the acceleration of this logic. It must tear itself from all referents and take pride only in the future. Theory must operate on time at the cost of a deliberate distortion of present reality.
~ Jean Baudrillard

To insure the adoration of a theorem for any length of time, faith is not enough, a police force is needed as well.
~ Albert Camus

The world can doubtless never be well known by theory: practice is absolutely necessary; but surely it is of great use to a young man, before he sets out for that country, full of mazes, windings, and turnings, to have at least a general map of it, made by some experienced traveler.
~ Lord Chesterfield

In order to shake a hypothesis, it is sometimes not necessary to do anything more than push it as far as it will go.
~ Denis Diderot

A theory is the more impressive the greater is the simplicity of its premises, the more different are the kinds of things it relates and the more extended the range of its applicability.
~ Albert Einstein

Creating a new theory is not like destroying an old barn and erecting a skyscraper in its place. It is rather like climbing a mountain, gaining new and wider views, discovering unexpected connections between our starting points and its rich environment. But the point from which we started out still exists and can be seen, although it appears smaller and forms a tiny part of our broad view gained by the mastery of the obstacles on our adventurous way up.
~ Albert Einstein

It is theory that decides what can be observed.
~ Albert Einstein

No theory is good unless it permits, not rest, but the greatest work. No theory is good except on condition that one use it to go on beyond.
~ Andre Gide

The wise man regulates his conduct by the theories both of religion and science. But he regards these theories not as statements of ultimate fact but as art-forms.
~ John B. S. Haldane

Theories that go counter to the facts of human nature are foredoomed.
~ Edith Hamilton

Unaware of the absurdity of it, we introduce our own petty household rules into the economy of the universe for which the life of generations, peoples, of entire planets, has no importance in relation to the general development.
~ Alexander Herzen

Even for practical purposes theory generally turns out the most important thing in the end.
~ Oliver Wendell Holmes

The temptation to form premature theories upon insufficient data is the bane of our profession.
~ Sherlock Holmes

A theory is no more like a fact than a photograph is like a person.
~ Edgar Watson Howe

A young man is a theory, an old man is a fact.
~ Edgar Watson Howe

Every theory is a self-fulfilling prophecy that orders experience into the framework it provides.
~ Ruth Hubbard

Everything that explains the world has in fact explained a world that does not exist, a world in which men are at the center of the human enterprise and women are at the margin ''helping'' them. Such a world does not exist -- never has.
~ Gerda Lerner

Delight at having understood a very abstract and obscure system leads most people to believe in the truth of what it demonstrates.
~ Georg C. Lichtenberg