Such a step, he said, would require only two stages; first, a passage out of the three-dimensional sphere we know, and second, a passage back to the three-dimensional sphere at another point, perhaps one of infinite remoteness. That this could be accomplished without loss of life was in many cases conceivable. Any being from any part of three-dimensional space could probably survive in the fourth dimension; and its survival of the second stage would depend upon what alien part of three-dimensional space it might select for its re-entry. Denizens of some planets might be able to live on certain others – even planets belonging to other galaxies, or to similar dimensional phases of other space-time continua – though of course there must be vast numbers of mutually uninhabitable even though mathematically juxtaposed bodies or zones of space.
It was also possible that the inhabitants of a given dimensional realm could survive entry to many unknown and incomprehensible realms of additional or indefinitely multiplied dimensions – be they within or outside the given space-time continuum – and that the converse would be likewise true. This was a matter for speculation, though one could be fairly certain that the type of mutation involved in a passage from any given dimensional plane to the next higher one would not be destructive of biological integrity as we understand it. Gilman could not be very clear about his reasons for this last assumption, but his haziness here was more than overbalanced by his clearness on other complex points. Professor Upham especially liked his demonstration of the kinship of higher mathematics to certain phases of magical lore transmitted down the ages from an ineffable antiquity – human or pre-human – whose knowledge of the cosmos and its laws was greater than ours.
Around 1 April Gilman worried considerably because his slow fever did not abate. He was also troubled by what some of his fellow lodgers said about his sleep-walking. It seemed that he was often absent from his bed and that the creaking of his floor at certain hours of the night was remarked by the man in the room below. This fellow also spoke of hearing the tread of shod feet in the night; but Gilman was sure he must have been mistaken in this, since shoes as well as other apparel were always precisely in place in the morning. One could develop all sorts of aural delusions in this morbid old house – for did not Gilman himself, even in daylight, now feel certain that noises other than rat-scratching came from the black voids beyond the slanting wall and above the slanting ceiling? His pathologically sensitive ears began to listen for faint footfalls in the immemorially sealed loft overhead, and sometimes the illusion of such things was agonizingly realistic.