Before I move on to discuss the other assumptions that generate the conclusion that there are no artefacts, I realise there is something else to discuss. This is the distinction between what Steven Savitt calls 'ontologically conservative' or 'retentive' theory change, or reductionism, and 'ontologically radical' or 'eliminitavist' theory change, or eliminativism. This is explained well here. Ontological conservatism is when we revise our view of the entities posited by the original theory, without eliminating them. For example, our conception of light was transformed by the discovery that it is electro-magnetic radiation, and older explanations of it had to be rejected as incorrect or incomplete or misleading. But this discovery did not lead to abandoning the existence of light. Ontological eliminativism is when we drop completely the view that certain entities exist. For example, there is nothing in modern psychology that justifies the existence of malevolent spirits or demons. So we dropped demons altogether from our modern scientific ontology.
This is closely connected with what I discussed here about Inwagen's paraphrase argument. If his paraphrase of a story about ships is intended merely to change our view about ships (e.g. that they are not identical with their component parts, and that there is something singular over and above the parts corresponding to the grammatically singular 'a ship') then the paraphrase is ontologically conservative. It still affirms the existence of ships, just as the electro-magnetic theory affirms the existence of light, but it changes our view of what ships are, just as the electro-magnetic story changes our view about light. By contrast, if the paraphrase really 'loses ships', then it is ontologically radical. It challenges our common-sense ontology in a way that modern psychology challenged demons.
It is also connected with the 'aporetic' set of propositions I discussed earlier. (I have modified proposition B to meet an objections made by earlier comments).
A. An artifact remains numerically the same if one of its components is replaced, without replacing the others.
B. If the components of X, are now the components of Y, arranged in the same way, then X=Y
C. Identity is transitive (if X=Y and Y=Z, then X=Z)
D. If artifact a and artifact b have numerically different components at the same time, a and b are numerically different.
E. Artifacts exist.
If the four propositions A-D are true, artefacts do not exist, which is the ontogically radical position. Otherwise, one of more of these four propositions is false. This would revise our view about the fundamental properties of artefacts, which is ontologically conservative. This is by way of background. I will return to the original plan tomorrow, when I will discuss whether modifying our account of numerical identity could resolve the logical inconsistency between the five propositions above.