ANGELS who talk with us do not talk in their own language but in ours, or in other languages in which we may be fluent—not in languages of which we have no knowledge. The reason for this is that when angels talk with us they turn toward us and unite with us; and one consequence of this union is that the two parties have much the same thought processes. Since our thinking is closely allied with our memory, and our language flows from it, the two parties share the same language. Further, when angels or spirits come to us and unite with us by turning toward us, they enter into our whole memory so completely that it seems exactly as though they themselves know everything we know, including our languages.
I have talked with angels about this and said that they might suppose they were talking with me in my own mother tongue simply because it seemed that way, when in fact it was not they talking but I. This follows from the fact that angels cannot utter a single word of our human language (Section 237). Then too, human language is natural and they are spiritual, and spiritual beings cannot produce anything natural. They have answered that they knew that when they were talking with us their union with us was with our spiritual thinking, but since this spiritual thinking flowed into our natural thought, and this natural thinking is so closely allied with our memory, it seemed to them as though our language were their own, along with all our acquired knowledge. This is because it has pleased the Lord that there should be this kind of union and inner presence of heaven with us. However, they said, the state of humanity is now such that this kind of union is no longer with angels but with spirits who are not in heaven.
I have talked with spirits about this matter, too; but they wanted to believe not that we were talking but that they were talking within us, so that we did not really know what we know, but they did, which meant that everything we knew came from them. I wanted to convince them by many arguments that this was not the case but failed.
We will explain later just who are meant by “angels” and who by “spirits,” when we come to our description of the world of spirits.
from Heaven and Hell, Section 246