A Device-Oriented Defi nition of Functions of Artifacts and Its Perspectives 207
type of function with a system function context a “component function.” The relationship
is hierarchical and is called “is achieved by,” as discussed in section 12.2.7.
In the appendix to our chapter, we try to show different notions of “context” in the lit-
erature by discussing other notions of context in contrast to our notion of context, and
then locating our notion in those other notions.
12.2.4 Capacity to Perform a Function
A function in our defi nition is a role played by a behavior, which is performed or realized
by a device. Such a performance is based on the device’s capacity to perform the function,
which is a feature (or property) of a device. For example, the heat-exchange behavior as
a basis of the heat-giving function mentioned before can be realized through high thermal
conductivity between channels of fl uids. A device with such physical properties could be
regarded as a thing that has a capacity to perform the heat-giving function. The capacity
to perform a function is potential and inherent in a device. It can be induced and performed
when an appropriate context and appropriate inputs are given to the device. The performed
function is restricted by the capacity to perform the function.
In the engineering literature, Hubka and Eder (1988) defi ne functions as follows: “The
function is a property of the technical system, and describes its ability to fulfi ll a purpose,
namely to convert an input measure into a required output measure under precisely given
condition.” In their defi nition, a purpose represents intended effects as output effects, while
a function is the actual ability for an internal task of the technical systems. Here purpose
and function roughly correspond to the function and capacity to perform a function in our
terminology, respectively.
In philosophy, a function is typically a special feature of artifacts or biological organs.
In particular, “[b]iological functions are typically taken as objective non-relational proper-
ties” (Vermaas this volume). In causal-role function analysis (Cummins 1975) and ICE
theory (Vermaas and Houkes 2006), a technical function is regarded as a special kind of
capacity (or disposition) to be ascribed to an artifact, as quoted in the appendix of this
chapter.
A function in our defi nition is a role of a behavior, which is rather independent of an
artifact, in contrast to the capacity, which is dependent on an artifact. In our defi nition,
the existence of a function as a role has two states according to its fulfi llment by a behavior.
When a user wants a function before actual use, the function partially exists as a required
function in a supposed context of use. By “partially-existing function” we mean that an
instance of a function as a role without a behavior (a role-player) and an artifact (a per-
former) is neither realized nor performed but exists just as a thing required by the user
within the specifi c context of use. Thus when a real artifact performs a behavior that plays
the function in the duration of use by a user in the specifi ed context, the function is per-
formed and then fully exists.^3 Hence the existence of such a partial function is dependent