420. Upon the earth, nor upon the sea, nor upon any tree, signifies everywhere in the spiritual world, even to its ultimates, in those who have any perception. This is evident from the signification of "the earth," as being the whole spiritual world, consequently all angels and spirits there. This is the signification of "the earth" in the general and nearest sense, because in the spiritual world, the same as on our globe, there are lands, mountains, hills, plains, valleys, and also seas (respecting which see above, n. 304, 342, 413). It is evident also from the signification of the "sea," as being the ultimates of the earth in the spiritual world, because the last boundaries or limits there are seas (respecting which see above, n. 342); also from the signification of "tree," as being perception and also knowledge (of which presently). This being the signification of "earth," "sea," and "tree," the three joined together in one idea signify all things in the spiritual world even to its ultimates in those who have any perception. A "tree" in general signifies perception and knowledge, because a "garden" signifies intelligence, and all intelligence is according to knowledges and a perception of them; this is why each kind of tree signifies something pertaining to knowledge [scientia] and intelligence. Because a "tree" signifies in general perception and knowledge, it also signifies the interiors of the mind with man, and also the whole man; for a man is such as are the interiors that belong to his mind, and these are such as is the perception from knowledges. (That a "tree" signifies the interiors that belong to the mind, and also man himself, see above, n. 109, 110; that a "tree" signifies perception and knowledge, see Arcana Coelestia 103, 2163, 2682, 2722, 2972, 7692; that the ancients had Divine worship in groves under trees, according to their significations, n. 2722, 4552; that this was prohibited with the Jewish nation, and why, n. 2722; that "paradises" and "gardens" signify intelligence, n. 100, 108, 3220; also in the work on Heaven and Hell 176; and above, n. 110)

3893. Angelic choirs were once praising the Lord and doing so with heartfelt joy. Their praises were heard sometimes as sweet singing, for to one another spirits and angels have resounding voices and they hear one another as well as men hear one another. But no human singing, however heavenly its sweetness and harmony, can compare with that of those angelic choirs. From the variety of sound I perceived that there were many choirs. I was told by the angels present with me that those choirs belonged to the province of the lungs and the functions of these, singing being their role because that is an activity of the lungs, as I was also given to know from experience. They were allowed to control my breathing, which was done so gently and softly and also interiorly that I was scarcely aware of myself breathing at all. I was also told that those assigned to involuntary breathing are distinct and separate from those assigned to voluntary. They said that those assigned to involuntary breathing were present when a person is asleep, for as soon as he is asleep his voluntary breathing stops and the involuntary takes over.