 Altruism is a well understood topic in evolutionary biology; the theoretical ideas explained above have been extensively analysed, empirically confirmed, and are widely accepted. Nonetheless, there are a number of conceptual ambiguities surrounding altruism and related concepts in the literature; some of these are purely semantic, others are more substantive. Three such ambiguities are briefly discussed below; for further discussion, see West et al. 2007, Sachs et al. 2004 or Lehmann and Keller 2006.