Morality is the theory that every human act must be either right or wrong, and that 99 % of them are wrong.
H. L. Mencken

A professor must have a theory as a dog must have fleas.
H. L. Mencken

Your theory is crazy, but it's not crazy enough to be true.
Niels Bohr

Land: A part of the earth's surface, considered as property. The theory that land is property subject to private ownership and control is the foundation of modern society, and is eminently worthy of the superstructure.
Ambrose Bierce

We are all agreed that your theory is crazy. The question which divides us is whether it is crazy enough to have a chance of being correct. My own feeling is that it is not crazy enough.
Niels Bohr

Rational behavior requires theory. Reactive behavior requires only reflex action.
W. Edwards Deming

I've got a theory that if you give 100% all of the time, somehow things will work out in the end.
Larry Bird

Philosophy is not a theory but an activity.
Ludwig Wittgenstein

Creationists make it sound as though a 'theory' is something you dreamt up after being drunk all night.
Isaac Asimov

Scientific views end in awe and mystery, lost at the edge in uncertainty, but they appear to be so deep and so impressive that the theory that it is all arranged as a stage for God to watch man's struggle for good and evil seems inadequate.
Richard P. Feynman

It doesn't matter how beautiful your theory is, it doesn't matter how smart you are. If it doesn't agree with experiment, it's wrong.
Richard P. Feynman

The theory that can absorb the greatest number of facts, and persist in doing so, generation after generation, through all changes of opinion and detail, is the one that must rule all observation.
Adam Smith

There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable.There is another theory which states that this has already happened.
Douglas Adams

My theory is that all of Scottish cuisine is based on a dare.
Mike Myers

In theory there is a possibility of perfect happiness: To believe in the indestructible element within one, and not to strive towards it.
Franz Kafka

The Dell Theory of Conflict Prevention argues that no two countries that are both part of the same global supply chain will ever fight a war as long as they are each part of that supply chain.
Thomas Friedman

Religion is essentially the art and the theory of the remaking of man. Man is not a finished creation.
Edmund Burke

Theory helps us to bear our ignorance of facts.
George Santayana

Read no history: nothing but biography, for that is life without theory.
Benjamin Disraeli

When a torrent sweeps a man against a boulder, you must expect him to scream, and you need not be surprised if the scream is sometimes a theory.
Robert Louis Stevenson