 One can produce other metaphysical arguments against the view that spacetime must be maximal. To demand maximality may lead to Buridan's Ass problems, for it can happen that global extensions exist in which one of a given set of incomplete curves is extendible, but no global extension exists in which every curve in the set is extendible (Ellis and Schmidt 1977). Also, there may exist several physically quite different global extensions: the spacetime covered by the usual Schwarzschild coordinates outside the Schwarzschild radius, for instance, can be extended analytically to Kruskal-Schwarzschild spacetime with a spacetime “tunnel” or “bridge” to an otherwise disconnected part of the universe (Hawking and Ellis 1973, sec. 5.5), or it can be extended to a solution representing the interior of a massive spherical body. It is, in any event, difficult to know what to make of the invocation of such overtly metaphysical considerations in arguments in this most hard of all hard sciences. See Curiel (1999) and Earman (1996) for critical survey of such arguments, and Doboszewski (2017) for a recent comprehensive survey of all these issues, including discussion of the most recent technical results. 