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.

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

4328. I have also been shown the situation in general with regard to the will part of the mind and the understanding part. The most ancient people who constituted the Lord's celestial Church, and who are described in 1114-1123, had a will which contained good and an understanding which contained truth derived from that good; and with them these two parts made one. The ancients however who formed the Lord's spiritual Church had a will that was completely destroyed, but an intact understanding within which, through regeneration, the Lord formed a new area of will, and through this a new area of understanding also, see 863, 875, 895, 927, 928, 1023, 1043, 1044, 1555, 2256.

[2] What the situation had been in the celestial Church so far as good was concerned was demonstrated by means of a blue-coloured column coming down from the sky, the left side of which was full of light, like the blazing light of the sun. This was a representation of the first state of those people, the blue colour representing their will, which was good, and the blazing light their understanding. After that the blue of the column turned to a dull red, which was a representation of their second state, a state in which their two kinds of life - that of the will and that of the understanding - still acted as one, though this was more dull so far as good from the will was concerned. For blue means good, and blazing light truth derived from good. After that the column became completely black, and surrounding the column there was a brightness which was variegated by means of something glittering and which presented colours. These changes meant the state of the spiritual Church. The black column meant that the will had been completely destroyed and that it was nothing but evil. The light variegated by something glittering meant the understanding in which a new will was provided by the Lord; for in heaven the understanding is represented by brightness.