"In addition to the social pressures from the scientific community there is also at work a very human trait of individual scientists. I call it the law of the instrument, and it may be formulated as follows: Give a small boy a hammer, and he will find that everything he encounters needs pounding. It comes as no particular surprise to discover that a scientist formulates problems in a way which requires for their solution just those techniques in which he himself is especially skilled. To select candidates for training as pilots, one psychologist will conduct depth interviews, another will employ projective tests, a third will apply statistical techniques to questionnaire data, while a fourth will regard the problem as a 'practical' one beyond the capacity of a science which cannot yet fully predict the performance of a rat in a maze. And standing apart from them all may be yet another psychologist laboring in remote majesty - as the rest see him - on a mathematical model of human learning.
"The law of the instrument, however, is by no means wholly pernicious in its working. What else is a man to do when he has an idea, Peirce asks, but ride it as hard as he can, and leave it to others to hold it back within proper limits? What is objectionable is not that some techniques are pushed to the utmost, but that others, in consequence, are denied the name of science. The price of training is always a certain 'trained incapacity': the more we know how to do something, the harder it is to learn to do it differently (children learn to speak a foreign language with less of an accent than adults do only because they did not know their own language so well to start with). I believe it is important that training in behavioral science encourage appreciation of the greatest possible range of techniques."
- Abraham Kaplan, The Conduct of Inquiry: Methodology for Behavioral Science, 1964
[possibly a variation on an unrecorded quote by Mark Twain]