Another explanation for the failure of logic and observation alone to advance medicine is that unlike, say, physics, which uses a form of logic - mathematics - as its natural language, biology does not lend itself to logic. Leo Szilard, a prominent physicist, made this point when he complained that after switching from physics to biology he never had a peaceful bath again. As a physicist he would soak in the warmth of a bathtub and contemplate a problem, turn it in his mind, reason his way through it. But once he became a biologist, he constantly had to climb out of the bathtub to look up a fact.

In fact, biology is chaos. Biological systems are the product not of logic but of evolution, an inelegant process. Life does not choose the logically best design to meet a new situation. It adapts what already exists...The result, unlike the clean straight lines of logic, is often irregular, messy.