Saul Kripke has claimed that there are necessary connections between material things and their material origins. The usual defences of such necessity of origin theses appeal to either a sufficiency of origin principle or a branching-times model of necessity. In this paper we offer a different defence. Our argument proceeds from more modest ‘independence principles’, which govern the processes by which material objects are produced. Independence principles are motivated, in turn, by appeal to a plausible metaphysical principle governing such processes, (...) their invulnerability to non-local prevention. We outline the new argument, and distinguish it from both of the usual defences. (shrink)