Michael Otsuka argues that collective pension schemes are forms of social cooperation on equal terms for mutual advantage and thus, matters of social justice. In this way Otsuka wants to understand collectively funded pensions in Rawlsian terms. I argue that not all forms of social cooperation are the same and that the specific kind of social cooperation Rawls has in mind is, in at least three central respects, different from the kind of social cooperation involved in the collective pension schemes Otsuka describes.