"Can you explain why it is that there are, at last count, sixteen schools of psychotherapy with sixteen theories of the personality and its disorders and that patients treated in one school seem to do as well or as badly as patients treated in any other - while there is only one generally accepted theory of the cause and cure of pneumococcal pneumonia and only one generally accepted theory of the orbits of the planets and the gravitational attraction of our galaxy and the galaxy M31 in Andromeda? (Hint: If you answer that the human psyche is more complicated than the pneumococcus and the human white-cell response or the galaxies or Einstein's general theory of relativity, keep in mind that the burden of proof is on you. Or if you answer that the study of the human psyche is in its infancy, remember then this infancy has lasted 2,500 years and, unlike physics, we don't seem to know much more about the psyche than Plato did.)"
- Walker Percy
Lost in the Cosmos: The Last Self-Help Book