12.7 Theory is the essence of experience; theories improve by being tested
For those who feel uneasy with 'grand' theories I have a word of reassurance. There is nothing more practical than a good theory: it is the essence of our knowledge in a ready-to-use form. No one can function efficiently without theoretical groundwork. I have come to this conclusion since it is apparent how easily people, even well established scientists, have been led astray by traditional but false expectations, dominant prejudices and quasi-obvious judgments. Especially in medicine we must draw upon different sources of knowledge to guide us in the diagnostic process and on the tortuous roads of therapy. Also outside the clinic, in a more general context, we rely on theories to direct our exploration of the world. Besides, there is nothing absolute about theories; they are continuously improved by empirical testing.
During the long period I've been hatching the contents for this book I've received enormous encouragement from my wife Titia. My colleagues Hans van Wijngaarden, Joop Wilms en Sjoeke van der Meulen have tolerated an occasional absence and have been patiently wondering what kind of bird would be hatched from the egg, since this could hardly be guessed after the disclosure of some wet feathers. Elisabeth Versteegh has contributed perceptive criticism and correction of style and language. From Don Williams and Gerlof van der Veen I have received valuable comments on an earlier version of the manuscript. Stan Tempelaars taught me how to appease a wayward computer. I thank them all for their support which has been indispensable.