An expert is a person who has found out by his own painful experience all the mistakes that one can make in a very narrow field. - Niels Bohr

An expert is a person who has made all the mistakes that can be made in a very narrow field.

An expert is a man who has made all the mistakes which can be made in a very narrow field.

There are some things so serious that you have to laugh at them.

I am absolutely prepared to talk about the spiritual life of an electronic computer: to state that it is reflecting or is in a bad mood... The question whether the machine really feels or ponders, or whether it merely looks as though it did, is of course absolutely meaningingless.

Everything we call real is made of things that cannot be regarded as real.