Page:Philosophy and Fun of Algebra.djvu/70

PHILOSOPHY AND FUN OF ALGEBRA and amused in thinking of other things; till he left off seeing things that were not there. But neither Macbeth nor his wife knew as much as Shakespeare did about the value of danger signals and the conditions for making a safe working hypothesis.

You had better read the story of Macbeth and see for yourselves what they did do.

Next to the old Hebrew books, Shakespeare is the best road map that I know of for people who wish to travel safely about the country of the imagination. 66