 According to what is probably the most influential argument in favor of PI over SI (an argument that changed Campbell’s mind: cf. his 1990: 55f.; cf. also Moreland 1985: 65), SI should be abandoned because it rules out the (non-empty) possibility that (parts of) reality could be  non-spatiotemporal.[20]  Against this, proponents of SI have argued that the thesis that reality must be spatiotemporal can be independently justified (primarily because naturalism can be independently justified, cf. Schaffer 2001: 251). And even if it cannot, SI could easily be modified to accommodate the analogue of the locational order of space (Campbell 1997[1981]: 136; Schaffer  ibid.).[21]