 As noted above, altruistic acts are guided by assumptions made by the agent about the well-being of some other individual or group. What well-being consists in is a disputed matter, but it is uncontroversial that a distinction must be drawn between (i) what constitutes well-being and (ii) what is a necessary means towards or a pre-condition of well-being. This kind of distinction is familiar, and is applicable in all sorts of cases. For example, we distinguish between what a breakfast consists in (cereal, juice, coffee) and the things one needs in order to eat breakfast (spoons, glasses, mugs). There is no such thing as eating breakfast but not eating anything that breakfast consists in. In the same way, well-being must be sought and fostered by seeking and fostering the good or goods in which well-being consists. Rival theories of well-being are competing ways of answering the question: what are its constituents? After we have answered that question, we need to address the further question of how best to obtain those constituents. (Contemporary discussions of well-being can be found in Badhwar 2014; Feldman 1994, 2010; Fletcher 2016; Griffin 1986; Kraut 2007; Sumner 1996 Tiberius 2018.)