Abstract

This paper inquires into the very possibility of the units of selection debate’s origin in the problem of altruism, function in articulating the evolutionary synthesis, and philosophical status as a problem in clarifying what makes something a level or unit of selection. What makes the debate possible? In terms of origins, there are a number of logically possible ways to deviate from the model of Darwinian individual selection to explain evolved traits. In terms of function, adherence to the evolutionary synthesis yields norms which restrict these possibilities to a manageable few. In terms of philosophical status, the abstract structure of selection mechanisms permits a causal construal, on which the unit of selection is identified with the “unit of possession”, that which possesses the causally efficacious trait selected for. It also allows a teleological interpretation, on which the unit of selection is identified with the “unit of benefit”, that for the sake of which the causally efficacious trait is selected. It is proposed that a unit of selection is really a pair of units, consisting of both a unit of possession and a unit of benefit.