I am looking for an exact quote from Jean Dieudonné saying more or less that
there are three kinds of important problems in mathematics:
problems of existence, classification and construction.
The quote may be in French or English, I guess I have read it in the forewords of one of his books, but I can't find it now. I also browsed his book "Pour l'honneur de l'esprit humain" without success.
EDIT: I am starting to doubt that it is a quote from Dieudonne. It could be from Andre Weil instead...