Similarly, many a young man, hearing for the first time of the refraction of stellar light, has thought that doubt was cast on the whole of astronomy, whereas nothing is required but an easily effected and unimportant correction to put everything right again.

Bodies do not produce sensations, but complexes of elements (complexes of sensations) make up bodies.

Scientists must use the simplest means of arriving at their results and exclude everything not perceived by the senses.

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.

The ego is as little absolutely permanent as are bodies.

Personally, people know themselves very poorly.

Thought experiment is in any case a necessary precondition for physical experiment. Every experimenter and inventor must have the planned arrangement in his head before translating it into fact.