Even for practical purposes theory generally turns out the most important thing in the end. – Oliver Wendell Holmes

I never guess. It is a shocking habit — destructive to the logical faculty. – Sir Arthur Conan Doyle

The temptation to form premature theories upon insufficient data is the bane of our profession. – Sir Arthur Conan Doyle

If there were no bad speculations there could be no good investments; if there were no wild ventures there would be no brilliantly successful enterprises. – F. W. Hirst