It is widely believed that Plato promoted a version of the "one over many" argument such that there would be Forms of all things. Among these Forms are also included those of artefacts. Aristotle denies, however, that Plato would accept such Forms. The ancient Platonic tradition is unusually unanimous in denying the existence of Forms of artefacts. This paper supports three main points: (a) through a careful examination of some Platonic texts (in particular Resp. 596a) it is possible to assert that he has never encouraged a version of the "one over many" that justifies the existence of Forms of all things; (b) the reductio ad unum defended by Plato can not be considered identical to Aristotle’s version of "one over many" argument; (c) there are some good textual and speculative reasons to deny the existence of Forms of artefacta. It is finally discussed a recent proposal by David Sedley, according to which Plato, in his mature works, accepted only Form of what has opposed properties and of artefacts (but not of natural things).