 Wybo Houkes and Pieter Vermaas (Houkes &amp; Vermaas 2004; 2010; Vermaas &amp; Houkes 2003) also have a mixed theory, although intentionalist factors predominate, in contrast to Millikan’s focus on non-intentionalist history of reproduction. Their approach is to derive a theory of artifact function from a theory of artifact use and design.