A theory is no more like a fact than a photograph is like a person.

A theory is no more like a fact than a photograph is like a person.

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.

Many things difficult to design prove easy to performance.

Many things difficult to design prove easy to performance.

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

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

It is the theory that decides what can be observed

It is the theory that decides what can be observed

Relativity applies to physics, not ethics

Relativity applies to physics, not ethics

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.

Conjecture as to things useful, is good; but conjecture as to what it would be useless to know, is very read more

Conjecture as to things useful, is good; but conjecture as to what it would be useless to know, is very idle.

Whenever a theory appears to you as the only possible one, take this as a sign that you have neither read more

Whenever a theory appears to you as the only possible one, take this as a sign that you have neither understood the theory nor the problem which it was intended to solve