Scientific controversies have a bad reputation these days. Instead of being viewed as an engine of scientific progress, they are seen by many scientists and others as clashes of unresolvable ideological differences in the way the world is perceived and understood. One of us long ago, as a know-it-all Harvard graduate student in conversation with other such graduate students, often referred to this or that controversy as an example of the “dialectic of polarized fanatics,” with the absolute but unspoken know-it-all understanding that there was little, if anything, useful taking place. More meaningfully perhaps, controversies are often said to generate “more heat than light” on a given scientific issue and, to this extent, to do little to advance understanding. To some observers, the debate over adaptationism in evolutionary biology has this character. From this perspective, the various views about the power of natural selection to shape phenotypes are so different that proponents of each talk past each other and often do not even acknowledge the potential validity of alternative views. Of course, one can still view such steadfastness as essential for the progress of science instead of as indicating an unproductive narrow-mindedness. One need not think that the debate over adaptationism is unresolvable or agree with either view as to the nature of ideological differences to appreciate the importance of refining our understanding of the meaning of adaptation and of optimality models.