It is widespread practice to define artefacts as entities that owe their existence to plan-based acts of production that aim at a certain use of the produced thing. According to this definition, artefacts are essentially intention-dependent. For this reason, artefacts are threatened by marginalisation within standard naturalised ontologies. I discuss three families of marginalisation strategies: elimination, reduction and supervenience. I argue that all of these strategies fail, as they lead to false implications, with the possible exception of four-dimensional supervenience, which (...) might well be true, but remains completely uninformative in respect to artefacts. The crucial issue in this regard is what Peter van Inwagen calls the Duplication Principle which is undermined by thought experiments involving chance entities or duplication. Hence, materialistic ontologies are not, as Peter van Inwagen wants us to believe, a Copernican revolution in ontology; they are simply not adequate for the domain of artefacts. (shrink)