Cooperation, ‘Ought Morally’, and Principles of Moral Harmony

There is a theory that one ought morally to do the best one can, when ‘best’ is suitably interpreted. There are also some examples in which, although every agent involved does the best she can, the group composed of them does not. Some philosophers think that these examples show the theory to be wrong. In particular, they think that such examples motivate a view which incorporates a requirement of cooperativeness in a particular way, though they disagree as to the exact nature of this requirement. This paper will argue both that such views are problematic and that the examples do not motivate departure from the original theory.