Abstract

It is widely assumed that a geometric model of boundaries, which prescribes a tripartite topological characterisation of the boundaries for material objects – fully open, fully closed, or partially open/closed – can be unproblematically extended from regions to material objects. Drawing on a disanalogy between regions and material objects – that only the latter move – I demonstrate the incoherence of (fully or partially) open material objects through two arguments relating to the ability for such objects to freely move. The first is a dilemma considering separately open material objects occupying their location directly or indirectly (located in virtue of their proper parts occupying locations). It is argued that movement in the former case would involve a miraculous topological transformation; whilst in the latter case, would involve miraculous reorganising movements in the object's proper parts. The second argument reignites a problem regarding the moment of change specifically for the movement of such objects.