 A second response is that the challenge requires a more sophisticated methodology. This may take the form of acknowledging explicitly the criteria that scientists use to assess desirability of scientific theories (Ellis 2007), which include considerations of explanatory power, consistency with other theories, and other factors, in addition to compatibility with the evidence. These come into conflict in unexpected ways in cosmology, and these different factors should be clearly articulated and weighed against one another. Alternatively, one might try to show that some of these desirable features, such as the ability to unify diverse phenomena, should be taken as part of what constitutes empirical  success.[59]  This leads to a more demanding conception of empirical success, exemplified by historical cases such as Perrin’s argument in favor of the atomic constitution of matter.