Without theory, practice is but routine born of habit.
He who loves practice without theory is like the sailor who boards ship without a rudder and compass and never knows where he may cast.
—Leonardo da Vinci
The quest for an explanation is a quest for theory.
Theories are the tools we use to understand the world. We must realize, however, that all theories are not created equal and that some ways of creating and verifying theories are better than others. The explanation that disease was caused by an imbalance of certain substances in the body, which could be rectified by blood-letting, was bogus. It was based on an invalid observation that human bodily fluids contained four “humors”—yellow ...