Diversity and disagreement are often thought to be obstacles that theories of justice must accommodate. Building on work by Lu Hong and Scott Page I argue that the relationship between diversity and justice is considerably more complicated than this. Certain sorts of diversity, namely diversity of the sort that manifests itself in disagreement over how similar various states of affairs are, can actually improve our chances of identifying better (or more just) states of affairs. This is particularly important if we think that justice is a non-monotonic evaluative metric – that is, a metric according to which worlds that are better in some respect are not necessarily better overall, even if other aspects of the world are held equal. Diversity also has real costs, though. The same considerations that lead us to disagree about how similar various states of affairs can also make it harder for us to communicate with one another. Furthermore, at some point disagreement regarding the similarity of states of affairs also gives us reason to think that we will disagree about the ways in which we evaluate those states of affairs. Diversity is thus both a curse and a blessing. A curse because it leads us to disagree about what states of affairs would be best. And a blessing because it improves our chances of identifying better states of affairs when we can agree about what these are.