The other day in Oxfam I found a tattered paperback copy of “The Psychology of Learning Mathematics”, by the late Professor Richard Skemp (who, incidentally, did his degree at Oxford and his Phd at Manchester, just like me!). It includes the following, which I liked so much I thought I’d share it:
There is an anecdote about a well-known professor of mathematics which, if it is not true, deserves to be. It relates that while addressing a learned audience, he wrote a mathematical statement on the board, saying “This, of course, is obvious”. Looking at it again, he said “At least I think it is obvious”. Growing more doubtful, he said “Excuse me,” and taking pencil and paper, was absent from the room for about twenty minutes. He returned beaming, and said triumphantly “Yes gentlemen, it is obvious.”