We come now to the question: what is a priori certain or necessary, respectively in geometry (doctrine of space) or its foundations? Formerly we thought everything; nowadays we think nothing. Already the distance-concept is logically arbitrary; there need be no things that correspond to it, even approximately.

As far as the laws of mathematics refer to reality, they are not certain, and as far as they are certain, they do not refer to reality.

Most teachers waste their time by asking question which are intended to discover what a pupil does not know whereas the true art of questioning has for its purpose to discover what pupils knows or is capable of knowing.

A new idea comes suddenly and in a rather intuitive way, but intuition is nothing but the outcome of earlier intellectual experience.

E=mc2. Energy equals mass times the speed of light squared. The original statement is: If a body gives off the energy L in the form of radiation, its mass diminishes by L/c2. Ist die Tragheit eines Korpers von Seinem Energieghalt Abhangig? 1905

We know nothing at all. All our knowledge is but the knowledge of schoolchildren. The real nature of things we shall never know.

With me every peep becomes a trumpet solo.