353. And I heard one of the four animals saying as with the voice of thunder, signifies out of the inmost heaven from the Lord. This is evident from the signification of "the four animals" or cherubim, as being in the highest sense, the Lord's Divine Providence and guard that there be no approach except through the good of love (of which see above, n. 152, 277); and as being in a relative sense the inmost and third heaven (of which see above, n. 313, 322); also from the signification of "the voice of thunder," as being the manifestation therefrom. That "lightnings," "thunders," and "voices," in the Word, signify illustration, understanding and perception, see above (n. 273), thence also manifestation. That "thunders" signify the manifestation from the inmost heaven is from correspondence; for the voices that come down out of that heaven even into the hearing of man are heard no otherwise, for they fill the whole cerebrum and extend themselves therefrom towards the hearing, and are there perceived as a sound of thunder. It is otherwise with the voices that come down from the middle heaven; for as these flow in with illustration, they are heard only sonorously like words of speech.

[2] The reason for this is that the things that come down out of the inmost or third heaven enter the will of man, and the will expresses itself in sounds; but the things that come down out of the middle of second heaven enter into the intellect of man, and the intellect expresses itself in articulations of sound; for sounds take form in the understanding, and sounds so formed, which are called articulations of sound, present themselves in the thought through ideas, and in the hearing through words. Those things, therefore, that come down out of the inmost or third heaven correspond to thunder, and those out of the middle or second heaven to lightning; and consequently in the Word "lightnings" and "thunders" signify illustration, understanding, and perception. There is something like this in the case of sounds in the world, which grow with an increase as they come down from heights, as from high mountains into valleys, and also from the clouds towards the earth, from which are thunders; so also the voices out of the third or highest heaven, when they roll on towards the lower parts and at length reach the lowest, in which is human hearing, are heard as thunders, but only by those whose interiors are opened, as John's were at this time.