For what I have accomplished and what I have become, I have to to thank my industry much more, my indefatigable working, rather than any outstanding ….

We are justified in calling numbers a free creation of the human mind..

That which is provable, ought not to be believed in science without proof..

"I see it, but I don't believe it.".

As professor in the Polytechnic School in Zürich I found myself for the first time obliged to lecture upon the elements of the differential calculus ….