In theory there is no difference between theory and practice. In practice there is.

In theory there is no difference between theory and practice. In practice there is.

You have to know you can first. How comes later.

You have to know you can first. How comes later.

You cannot run a business, or anything else, on a theory.

You cannot run a business, or anything else, on a theory.

It is the theory that decides what can be observed

It is the theory that decides what can be observed

Let us work without theorizing, 'Tis the only way to make life endurable.

Let us work without theorizing, 'Tis the only way to make life endurable.

In scientific work, those who refuse to go beyond fact rarely get as far as fact.

In scientific work, those who refuse to go beyond fact rarely get as far as fact.

A young boy is a theory, an old man is a fact.

A young boy is a theory, an old man is a fact.

I never once made a discovery ... I speak without exaggeration that I have constructed three thousand different theories in read more

I never once made a discovery ... I speak without exaggeration that I have constructed three thousand different theories in connection with the electric light ... Yet in only two cases did my experiments prove the truth of my theory.

Our theories of the eternal are as valuable as are those which a chick which has not broken its way read more

Our theories of the eternal are as valuable as are those which a chick which has not broken its way through its shell might form of the outside world.