"Experts often arrive at different results, both in fundamental matters, and in application Who does not know of at least one case in his family where one doctor recommends a certain operation, another argues against it, while a third suggests an entirely different procedure? Who has not read of the debates about nuclear safety, the of the economy, the effects of pesticides, aerosol sprays, the efficiency of methods of education, the influence of race on intelligence? Two, three, five and even more views arise in such debates, and scientific supporters can be found for all of them. Occasionally one almost feels inclined to say: as many scientists, as many opinions. There are of course areas in which scientists agree- but this cannot raise our confidence. Unanimity is often the result of a political decision: dissenters are suppressed, or remain silent to preserve the reputation of science as a source of trustworthy and almost infallible knowledge. On other occasions, unanimity is the result of shared prejudices: positions are taken without detail examination of the matter under review and are infused with the same authority that proceeds from detailed research."