Realism and Artifact Kinds 197
input-output notion of “function”—most of the time leaving implicit the input
conditions.
The System of Interaction specifi es the conditions in which the object is expected to
realize a certain output starting from a given input—the output being some fi nal status or
activity concerning the system or some of its parts. The System of Interaction specifi es all
the relevant interactions with other objects and is particularly important for specifying the
notion of use of an artifact. An artifact is conceived by its author and also by users as
something that, used in a certain way, can bring about a certain result. Moreover, the
System of Interaction is also relevant for assessing the functioning of the object. Among
the classical requirements for a theory of function, there is what is known as the “mal-
functioning requirement.” We say, for example, that a chair is a malfunctioning chair if it
is so unstable that a human being with a normal constitution can hardly sit on it, at least
if the chair is being used in the right conditions. Let us, for example, consider the case of
a chair standing on an uneven fl oor. Even if such a chair would equally prove to be
unstable, we would be more cautious about calling it a malfunctioning chair. The reason
lies in the fact that even if most of the time malfunctioning judgments seem to involve
only an input-output characterization of function, they also actually presuppose that the
object is properly used. We cannot say that a misused object is malfunctioning—strictly
speaking, we simply do not know.^8 The System of Interaction provides the correct condi-
tions of use for the artifact.
A further point is that the right conditions of use do not always involve an intentional
notion of “use.” For certain artifacts, it is not clear if we can say that their proper use is
intentional, while for other artifacts even if there is an intentional use it is not clear if it
is the intentional use that is relevant to the assessment of their functional properties. For
example, a guardrail is something that has to be installed in the right way to perform its
function, and this can be regarded as an intentional use. Still the proper function of the
guardrail is to prevent vehicles—specifi ed for ranges of velocity, weight, trajectory of
impact, and so forth—from going off the road. The conditions in which the guardrail is
expected to perform its function of stopping vehicles that hit it do not entail intentional
use. When someone loses control of his or her car the properly functioning guardrail must
be able to keep the car on the road: there is no intentional use.
For those claiming that an artifact is an object produced for a certain use, the
problem is to adopt a notion of “use” that is suffi ciently broad to include cases of
nonintentional interaction between the user and the artifact, as in the case of the guardrail.
Cases of artifacts produced for nonintentional interaction with the user are even more
frequent at the artifact-component level: practically every mechanical or electric device is
made of components that have been built to perform a function, but not for intentional
use, at least not in the same sense in which chairs and tables are used. The System of
Interaction specifi es the right conditions for the object to perform the function and to be
used.