1610. The interior heaven is therefore in degree within the world of spirits, for the world of spirits is separated from heaven, because the world of spirits derive what pertains to them from corporeal things, consequently they are conjoined with things corporeal and worldly, or rather [I may say] the world of spirits stands related to corporeal things as does the crasser atmospheric world to the terraqueous; wherefore the world of spirits occupies the interiors of corporeal things.