 Second, the more traditional philosophers of science would like to see Bayesians contribute to some classic debates, such as the one between scientific realism and anti-realism. Scientific realism is, roughly, the view that we have good reason to believe that our best scientific theories are true, literally or approximately. But the anti-realists disagree. Some of them, such as the instrumentalists, think that we only have good reason to believe that our best scientific theories are good tools for certain purposes. Bayesians often compare the credences assigned to competing scientific theories, but one might like to see a comparison between, on the one hand, the credence that a certain theory T is true and, on the other hand, the credence that T is a good tool for such and such purposes.