However, since we have broken this connection by turning our inward natures away from heaven and toward the world and ourselves through our self-love and love of the world and have so pulled away that we no longer serve heaven as its basis and foundation, the Lord has provided a medium to serve in place of that basis and foundation and to maintain the union of heaven with humanity. That medium is the Word.
Just how the Word serves as that medium, though, has been shown at length in Secrets of Heaven, with pertinent material collected in the booklet The White Horse Described in the Book of Revelation.
I have been told from heaven that the earliest people had direct revelation because their inner natures were turned toward heaven, and that this was the source of the Lord’s union with the human race at that time. After those times, though, there was not the same kind of direct revelation, but an indirect revelation through correspondences. All their divine worship consisted of these; so the churches of those times were called symbolic churches. They knew what correspondences and representations were and that everything on earth answered to spiritual things in heaven and the church (or represented them, which amounts to the same thing). In this way, the natural elements that constituted their outward worship served them as means for thinking spiritually and therefore thinking with angels.
Once all knowledge of correspondences and representations had been lost, then a Word was written in which all the words and the meanings of the words are correspondences and therefore contain that spiritual or inner meaning in which angels are engaged. So when we read the Word and grasp it in its literal or outward meaning, angels grasp it in its inner or spiritual meaning. In fact, all the thought of angels is spiritual, while ours is natural. These two kinds of thought do seem different, but they are one because they correspond.
This is why, after we had moved away from heaven and broken the connection, the Lord provided that there should be a means of union of heaven with us through the Word.
from Heaven and Hell, Sections 305, 306