Assumptions

Your assumptions are your windows on the world. Scrub them off every once in a while, or the light wont come in. – Alan Alda

Treat with utmost respect your power of forming opinions, for this power alone guards you against making assumptions that are contrary to nature and judgments that overthrow the rule of reason. – Marcus Aurelius

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

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

Another great evil arising from this desire to be thought rich; or rather, from the desire not to be thought poor, is the destructive thing which has been honored by the name of speculation; but which ought to be called Gambling. – William Cobbett

The narrower the mind, the broader the statement. – Ted Cook

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

I never guess. It is a shocking habit — destructive to the logical faculty. – Sir Arthur Conan Doyle

The temptation to form premature theories upon insufficient data is the bane of our profession. – Sir Arthur Conan Doyle

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

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

Choose an attitude of wonderment, taking in all that is being said without assuming you already know what the speaker is talking about. Let go of jumping ahead to finish his or her thoughts. In order to learn you have to risk change…changing your mind! – Dwight Frindt

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

If the world were good for nothing else, it is a fine subject for speculation. – William Hazlitt

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

If there were no bad speculations there could be no good investments; if there were no wild ventures there would be no brilliantly successful enterprises. – F. W. Hirst

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