Classification always has to simplify, asserting the importance of some attributes of an artifact, for example, over others. Taxa or classes are characterised by relative homogeneity. The heterogeneous is that which escapes or embarrasses the procedures of classification. Alterity and otherness are closely related terms which refer to what is in opposition to a particular phenomenon and so, by being different, give shape to it and mark its boundaries. In sexist discourse for example masculinity may be defined by the expulsion of what it is not, the feminine; the feminine becomes the other. For Bataille heterogeneity refers to a whole range of unassimilable experiences and phenomena such as sexuality, excretion, destruction, bestiality, ecstasy, trance, which are often the focus of sacred energies and taboo.

Heterogeneity and alterity are important interpretive terms because they refer to the relative independence of what it is we are trying to understand (it always somehow escapes us), remind us that there is always more to learn, that any classification or typology is provisional. The concepts also point to the perpetual presence of horror in social experience — that which cannot be rationally assimilated.