8. Controversies
''A professor'' it has been said ''is one who thinks otherwise.'' Thinking otherwise, questioning orthodoxy, and challenging conventional wisdom are essential components of the tool kit of science. For though science grows largely by personal curiosity, its refinement requires personal skepticism and individual doubt. Doubt arises when existing explanations prove inadequate to account for personal experience, and especially when new data and new experiences impose an additional strain upon existing explanations. Doubt is resolved either by new experience, and especially the contrived experience that we call experiment, or by a comparison of individual experiences and competing explanations, involving at times intense debate, which in turn allows a modification of detailed explanation or general theory. One aspect of verification in science is that experiments are always described and published in such a way that they may be repeated by any trained observer who chooses to duplicate them. This opening of private experience to public scrutiny is the ultimate basis for the large body of agreement that characterizes the scientific world, as well as its classic disputes.
Because much of this debate takes place in public, the history of science is inevitably marked by a good deal of spirited controversy. Some of this has been deeply personal, for many scientists find it difficult to avoid a paternalistic attitude toward their own discoveries and explanations. Other bitter controversies have involved the non-scientific implications of scientific discoveries, and there have been relatively frequent debates between scientists and those of other groups. Still other controversies have wracked the whole scientific world, and their resolution has produced significant turning points in the history of scientific thought. The controversies regarding the nature of the universe following publication of Copernicus's work and those concerning the organic world following publication of Darwin's Origin of Species are cases in point. Because the effect of such disputes as these is often to change the whole scientific framework in which explanation is offered, such major controversies are rarely settled quickly; indeed some of them may extend over decades. The notion of continental drift, for example, was first suggested on the basis of scientific evidence in a map published by Antonio Snyder in 1855, but it was at first ignored and then later ridiculed, especially during the middle years of the twentieth century. It was only the availability of new information in the form of paleomagnetic anomalies, and the development of the embracing concept of plate tectonics in the late 1960s, that provided general acceptance for a much modified theory of continental drift.