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)

6651. 'And a new king arose over Egypt' means separated factual knowledge, which is opposed to the Church's truths. This is clear from the representation of Pharaoh, to whom 'king' refers here, as factual knowledge in general, dealt with in 6015. The word 'king' is used because in the genuine sense 'king' means truth, 1672, 2015, 2069, 3670, 4581, 4966, 5044, 6148, and in the contrary sense falsity; and since 'king' refers here to Pharaoh, false factual knowledge is meant, that is, factual knowledge that is opposed to the Church's truths. This also explains why the expression 'new king' is used, for the one who lived in Joseph's time represented factual knowledge that accorded with the Church's truths. For the meaning of 'Egypt' as factual knowledge, here that knowledge in particular, see above in 6638.