Existence Quote by Thomas Huxley

The whole [scientific] process resembles biological evolution. A problem is like an ecological niche, and a theory is like a gene or a species…

— David Deutsch

A theory must be tempered with reality.

— Jawaharlal Nehru

Every theory presented as a scientific concept is just that; it's a theory that tries to explain more about the world than previous theories…

— Marvin Harris

The theoretical idea ... does not arise apart from and independent of experience; nor can it be derived from experience by a purely logical…

— Albert Einstein

I'm not sure what theory is, unless it's the pursuit of fundamental questions.

— David Antin

The important question is whether [a theory] is true, not whether envisioning an alternative is too intellectually painful to bear.

— J. D. Trout

Meanwhile, the originator of a theory may have a very lonely time, especially if his colleagues find his views of nature unfamiliar, and difficult…

— Peter D. Mitchell

Theory is good; but it doesn't prevent things from existing.

— Jean-Martin Charcot

Theory may be deliberate, as in a chapter on chemistry, or it may be second nature, as in the immemorial doctrine of ordinary enduring…

— Willard Van Orman Quine

There is such a difference between life and theory.

— Anthony Trollope

Creating a new theory is not like destroying an old barn and erecting a skyscraper in its place. It is rather like climbing a…

— Albert Einstein

It is a condition which confronts us-not a theory.

— Grover Cleveland