 We can focus our attention either on individual features that humans possess and animals lack, and that might be thought relevant to their inclusion within the scope of justice, or on asymmetries in the relationship between humans and other animals. To begin with the latter, Hume claimed that the domination humans exercised over animals – such that an animal could only possess something by virtue of our permission – meant that we were ‘bound by the laws of humanity to give gentle usage to these creatures, but should not, properly speaking, lie under any restraint of justice with regard to them’ (Hume, Enquiry, p. 190). For Rawls and those influenced by him, principles of distributive justice apply among agents who are related to one another as participants in a ‘cooperative venture for mutual advantage’, and this might seem to exclude animals from the scope of such principles. Critics of this view have pointed to cases of human-animal co-operation (Donaldson and Kymlicka 2011, Valentini 2014); however these arguments focus mainly or entirely on the special case of dogs, and it seems implausible to generalise from them in an attempt to show that human-animal relationships generally have a co-operative character.