The "midst" of something in the Bible represents the thing that is most central and most important to the spiritual state being described, the motivation that drives everything else. In general this will be something we love or feel, because at the core of things we are what we love; our loves define us.

(参考: Apocalypse Revealed 44, 90, 268; Arcana Coelestia 2252, 2940, 10153, 10365, 10557, 10635, 10641)

61. Everything that has to do with cognitions of faith is called spiritual, and everything that has to do with love to the Lord and towards the neighbour is called celestial. The former belong to man's understanding, the latter to his will.