In questions of science the authority of a thousand is not worth the humble reasoning of a single individual. I do not feel obliged to believe that the same God who has endowed us with sense, reason, and intellect has intended us to forgo their use. -- Galileo Galilei
Textbooks present science as a noble search for truth, in which progress depends on questioning established ideas. But for many scientists know from bitter experience that disagreeing with the dominant view is dangerous - especially when that view is backed by powerful interest groups.