In science fiction ideas about human subjectivity and identity have traditionally been established in a comparison between self (human) and Other (non-human) characters. So, the alien, monster or robot of science fiction may provide an example of Otherness, against which a representation of ‘proper’ human subjectivity is established, interrogated and, on occasion, problematised. Images of Otherness in science fiction can be understood as a metaphor for forms of Otherness within society or between societies and in this way the genre can engage with the fears and anxiety surrounding a given society's Others. Preceding chapters have concentrated on the representation of gender and sexuality, but received notions of human subjectivity and identity are also bound up with issues surrounding race and ethnicity. Based upon classificatory models largely constructed in the nineteenth century, qualities and traits have often been assigned to particular races with the assumption that the race in question is homogenous and that individuals belonging to various racial groupings are the vessels of essential racial characteristics. So racial markers, as with the markers of sexuality, are frequently referred to as ‘evidence’ of an essentialised being that is separate and divided from other modes of being. However, divisions between self/Other have not always been based upon models of a clear cut opposition. For instance, as Robert J. C. Young points out: