A series of explanatory hypotheses are examined under the assumption that the logical structure of function attributions is dependent on the methodological constraints which these hypotheses conform to. Two theses are argued for: (1) Given these methodological constraints, if something has the function of doing Y, then normally it is the only kind of thing that can do Y in that kind of system. (2) What distinguishes function attributions from causal attribution is not that function attributions explain the etiology of (...) the causally efficacious object, as Wright has suggested. The distinction lies rather in that the object's having the effect, which is attributed to it as its function, must figure in the explanation of why it does what it does to achieve that effect. (shrink)