 There is another area of investigation intimately related to issues of Cosmic Censorship in general, and issues of determinism in general relativity in particular: whether or not spacetime is “hole-free”. This has been the subject of recent philosophical work, primarily by Manchak (2009b, 2014a, 2016a). Geroch (1977) originally proposed the idea of a generic “hole” in spacetime in trying to capture in as general terms as possible the idea that spacetime has no obstruction of any kind that would prevent it from “evolving as far into the future as it reasonably could”. (Recall the discussion of maximality and extendibility in  section 1.1.)  Although Geroch's definition had powerful conceptual appeal, in the event it has proven untenable: Krasnikov (2009) showed that, according to it, even Minkowski spacetime fails to be hole-free. Manchak (2009b) showed how an emendation of Geroch's definition could fix the problem. He then showed that, under the assumption of global hyperbolicity (a strong condition of causal well-behavedness for a spacetime), one gets a nice hierarchy of conditions relating to determinism: geodesic completeness implies effective completeness (Manchak's own condition), which implies inextendibility, which implies hole-freeness (Manchak 2014a; see  section 1.1  for the definitions of these conditions). In related work, Manchak (2014b) showed that, in a sense one can make precise, it should be easier to construct a machine that would result in spacetime's having such a hole than one that would result in time-travel. In short, creating the possibility for indeterminism seems easier in the theory than the possibility for causal paradox! 