On Unifi cation: Taking Technical Functions as Objective 75
5.4 Constructing Ontological Function Theories
In Cummins’s theory, functions—biological, technical, and others—are defi ned as
follows.
Cummins’s function theory
x functions as a φ in s (or: the function of x in s is to φ) relative to an analytical
account A of s’s capacity to ψ just in case x is capable of φ-ing in s and A
appropriately and adequately accounts for s’s capacity to ψ by, in part, appealing to
the capacity of x to φ in s. (1975: 762)
Here s is a “containing system” that has the functionally described item x as its part in a
broad sense: s may, for instance, be a physical object or a process, and so may x, in any
combination. The analytical account A refers to an explanation of the capacity to ψ of s
in terms of, in part, x’s capacity to φ.
A fi rst remark is that in Cummins’s theory, functions refer to capacities and not to pur-
poses, as may be the case in intentional function theories. A second remark is that it is not
clear if Cummins’s theory is an epistemic or ontological function theory (Houkes and
Vermaas 2009). The reference to the account A suggests taking Cummins’s theory epis-
temically as one that says that agents can ascribe capacities as functions to items if these
capacities fi gure in explanations based on account A that s has its capacity to ψ. Yet the
usual understanding is that Cummins’s theory identifi es functions as causal contributions:
functions of items are capacities that causally contribute to s’s capacity to ψ. This under-
standing suggests taking the theory more ontologically as one about reality independent
of the account A. This ambiguity becomes manifest when one explicitly interprets Cum-
mins’s theory as an epistemic theory about agents who by account A ascribe functions,
and contrasts this with an interpretation in which Cummins’s theory is about functions
items have relative to containing systems but independent of the account A.
An epistemic interpretation of Cummins’s theory
Agent a justifi ably ascribes the capacity to φ as a function to x relative to the capacity
to ψ of s and relative to an analytical account A of s’s capacity to ψ iff x is capable
of φ-ing in s and agent a is justifi ed to believe on the basis of A that this capacity to
φ of x in s causally contributes to s’s capacity to ψ.
An ontological interpretation of Cummins’s theory
Item x has the capacity to φ as a function relative to the capacity to ψ of s iff item x
is capable of φ-ing in s and this capacity to φ of x in s causally contributes to s’s
capacity to ψ.
Note that in the epistemic interpretation, the account A provides only justifi cation for the
agent’s belief that x’s capacity to φ causally contributes to s’s capacity to ψ; by Cummins’s