To us investigators, the concept ‘soul’ is irrelevant and a matter for laughter. But matter is an abstraction of exactly the same kind, just as good and just as bad as it is. We know as much about the soul as we do of matter.

Science is the most complete presentment of facts with the least expenditure of thought.

Thing, body, matter, are nothing apart from the combinations of the elements, – the colours, sounds, and so forth – nothing apart from their so-called attributes.

Strange as it may sound, the power of mathematics rests on its evasion of all unnecessary thought and on its wonderful saving of mental operations.

What Mach calls a thought experiment is of course not an experiment at all. At bottom it is a grammatical investigation.

Science is the most complete presentment of facts with the least expenditure of thought

I can accept the theory of relativity as little as I can accept the existence of atoms and other such dogmas.

Science itself, therefore, may be regarded as a minimal problem, consisting of the completest possible presentment of facts with the least possible expenditure of thought.

Physics is experience, arranged in economical order.

The mathematician who pursues his studies without clear views of this matter, must often have the uncomfortable feeling that his paper and pencil surpass him in intelligence.