The reason why glorification from the celestial kingdom is signified by thunder is, that from it there are not heard expressions of speech, but only sounds. The reason is, that all those who are in that kingdom speak from love, or from affection, which proceeds from the heart; and such speech, when it flows down from that heaven to those below, is heard as thunder. For all affections, in the spiritual world, are heard as sounds, with their variations; while the thoughts therefrom are made evident by the articulations of sound, called words; upon this subject see what is said above (n. 323, 393); and in the work concerning Heaven and Hell (n. 234-245). But all those who are in the spiritual kingdom speak from thought, which belongs to the understanding, or the soul (anima); and when such speech flows down out of heaven to the parts below, it is heard either as a voice, or as harmonious music, or is seen as the brightness of a cloud, or as flame like that of lightning before thunder. This is why lightnings, thunders, and voices, in the Word, signify enlightenment, understanding, and perception, as may be seen above (n. 273, 702, 704); and that voices sent down from the celestial kingdom are heard as thunder (n. 353, 393, 821).