74 Pieter E. Vermaas
a can on the basis of the ontological theory justifi ably ascribe φ as a function that x has
relative to its design. If, conversely, a is justifi ed to ascribe the purpose φ as a function
that an artifact x has relative to its design, then a can on the basis of the ontological theory
justifi ably believe that x was designed for purpose φ. Hence one can arrive with the second
ontological design function theory at the following associated epistemic function theory.
An epistemic function theory associated with the ontological design function theory
Agent a justifi ably ascribes the purpose φ as a function that the artifact x has relative
to its design iff agent a is justifi ed to believe that x was designed for purpose φ.
This third epistemic technical functions theory is a special case of the fi rst epistemic theory,
because now the theory is explicitly one about functions as relations that artifacts have.
Moreover, in the second ontological design function theory and its third epistemic associ-
ate, technical functions are ontologically subjective and epistemically objective: the mode
of existence of technical functions of artifacts depends in these theories on the mental
states of the designers of the artifacts, and the truth or falsity of judgments about whether
artifacts have specifi c technical functions, that is, whether they are designed by their
designers for specifi c purposes, does not depend on the attitudes, feelings, and points of
view of the makers and the hearers—the agents a—of these judgments.
There thus exist ontological theories for technical functions in which these functions
are epistemically objective. If such ontological theories are acceptable, the differences
between biological and technical functions are to a large extent avoided: technical func-
tions are then also epistemically objective relations that artifacts have relative to context.
The above ontological design function theory is probably not acceptable, say within
archaeology, since its application presupposes that agents typically have the means to
determine for which purposes artifacts were designed originally. Neander’s function theory
for artifacts, briefl y mentioned in section 5.2, may be taken as a modifi cation of the onto-
logical design function theory aimed at circumventing this presupposition since in that
theory technical functions are also determined by the intentions of users, making it also
applicable to artifacts of which it is not clear for what purpose they were designed, but
that are nevertheless currently used for specifi c purposes. Note, however, that in Neander’s
theory, technical functions can be epistemically subjective: an artifact x can have a purpose
φ as a function if an agent retains x for that purpose, hence for that agent the truth of the
judgment that x has this function φ depends on the point of view this agent takes toward
the artifact. Neander’s function theory thus does not limit the differences between biologi-
cal and technical functional descriptions to the extent I wish to do in this contribution.
In the next section I analyze Cummins’s function theory and formulate a general strategy
to construct with epistemic technical function theories ontological theories in which judg-
ments about technical functions are epistemically objective. In section 5.5 I apply this
strategy to the ICE theory.