Preconceived ideas are like searchlights which illumine the path of the experimenter and serve him as a guide to interrogate nature. They become a danger only if he transforms them into fixed ideas-this is why I should like to see these profound words inscribed on the threshold of all the temples of science: 'The greatest derangement of the mind is to believe in something because one wishes it to be so.'
What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
No one believes an hypothesis except its originator but everyone believes an experiment except the experimenter.
I don't think that somebody who is observing or predicting behavior should also be participating in the 'experiment.'
It is necessary to look at the results of observation objectively, because you, the experimenter, might like one result better than another.
Men who believe too firmly in their theories, do not believe enough in the theories of others. So ... these despisers of their fellows ... make experiments only to destroy a theory, instead of to seek the truth.
