For something to be cast down or cast out generally refers to a rather dramatic move from a higher spiritual state to a lower one. In most cases it's used in reference to evil desires or false thinking – or people spreading desires and false thinking – being removed and banished, even condemned to hell. Some uses are more moderate, though, and sometimes – when Moses casts down his rod in performing a miracle, for example – it signifies the sudden inflowing of the divine into the natural world.

(References: Apocalypse Explained 497, 1175; Apocalypse Revealed 252, 552, 835, 872; Arcana Coelestia 2657, 6693, 6948; The Apocalypse Explained 1181)

1175. Verse 19. And they cast dust upon their heads and cried out weeping, and mourning, signifies grief and confession that by a life according to that religious persuasion and its doctrine they were condemned. This is evident from the signification of "to cast dust upon the head," as being to mourn because they were condemned (it follows as a consequence that it was on account of life according to that religious persuasion and its doctrine); also from the signification of "to cry out weeping and mourning," as being grief that they were condemned by such a life, "to cry out" having reference to doctrine, and "to weep and mourn" signifying grief of soul and heart (as above, n. 1164. "To cast dust upon the heads" means mourning on account of condemnation, because "dust" signifies what is condemned, and "head" the man himself. "Dust" signifies what is condemned, because the hells are beneath and the heavens are above, and from the hells falsity from evil unceasingly breathes forth, consequently the dust over them signifies what is condemned (See also above, n. 742. Because of this signification of "dust" it was a custom in the representative churches to cast dust upon their heads when they had done evil and had repented of it, thus giving proof of their repentance.

[2] That this was so can be seen from the following passages. In Ezekiel:

They shall cry bitterly and shall cast up dust upon their heads, they shall roll themselves in ashes (Ezekiel 27:30).

"To cast up dust upon their heads" signifies mourning because of condemnation, and "to roll themselves in ashes" signifies still deeper mourning, for "ashes" signify what is condemned, because the fire from which they come signifies infernal love. In Lamentations:

The elders of the daughter of Zion sit upon the earth, they keep silence, they have cast up dust upon their heads; the virgins of Jerusalem hang down their heads to the earth (Lamentations 2:10).

By such things grief and mourning because of evils and falsities of which they repented, and thus confession that they were condemned, were represented. "Daughter of Zion" signifies the church, and "virgins of Jerusalem" signify truths of doctrine; "to sit upon the earth and keep silence" signifies grief of mind; "to cast dust upon the head" signifies confession that they were condemned, and "to hang down the head to the earth" signifies confession that they were in hell. In Job:

The friends of Job rent everyone his mantle, and sprinkled dust upon their heads toward heaven (Job 2:12).

"To sprinkle dust upon the head towards heaven" signifies mourning on account of Job, who seemed to be condemned. Mourning on account of condemnation of evil is signified by "dust upon the head," and "rending the mantle" signifies mourning on account of condemnation of falsity. The same is signified by:

Rolling themselves in the dust (Micah 1:10).

That repentance was thus represented is evident in Job:

I repent upon dust and upon ashes (Job 42:6).

Because "dust" signifies condemnation, it was said to the serpent:

Upon the belly shalt thou go, and dust shalt thou eat all the days of thy life (Genesis 3:14).

The "serpent" signifies infernal evil with those who pervert the truths of the Word, and thereby deceive artfully and craftily. So in Isaiah:

Dust shall be the serpent's bread (Isaiah 65:25).

From all this it is clear that "dust" signifies what is condemned, and that "to cast dust upon the head" is a testification of condemnation.

(Continuation)

[3] All this having been premised it shall now be told what affection is, and afterwards why man is led by the Lord by means of affections and not by means of thoughts, and lastly that man can be saved in no other way.

What affection is. The same is meant by affection as by love. But love is like a fountain and affections are like the streams therefrom, thus affections are continuations of love. Love as a fountain is in the will of man; affections, which are streams from it, flow by continuity into the understanding, and there by means of light from truths produce thoughts, just as the influences of heat in a garden produce germinations by means of rays of light. Moreover, love in its origin is the heat of heaven, and truths in their origin are the rays of light of heaven, and thoughts are germinations from their marriage.

From such a marriage are all the societies of heaven, which are innumerable, which in their essence are affections; for they are from the heat that is love and from the wisdom that is light from the Lord as a sun. Therefore these societies, as heat in them is united to light, and light is united to heat, are affections of good and truth. From this are the thoughts of all in these societies. This makes clear that the societies of heaven are not thoughts but affections, consequently to be led by means of these societies is to be led by means of affections, that is, to be led by means of affections is to be led by means of societies; and for this reason in what now follows the term affections will be used in place of societies.

[4] Why man is led by the Lord by means of affections and not by means of thoughts shall now be told. When man is led by the Lord by means of affections he can be led according to all the laws of His Divine providence, but not if he should be led by means of thoughts. Affections do not become evident to man, but thoughts do; also affections produce thoughts, but thoughts do not produce affections; there is an appearance that they do, but it is a fallacy. And when affections produce thoughts they produce all things of man, because these constitute his life. Moreover, this is known in the world. If you hold a man in his affection you hold him bound, and lead him wherever you please, and a single reason is then stronger than a thousand. But if you do not hold man in his affection reasons are of no avail, for his affection, when not in harmony with them, either perverts them or rejects them or extinguishes them. It would be similar if the Lord should lead man by means of thoughts immediately, and not by means of affections.

Again, when a man is led by the Lord by means of affections, it seems to him as if he thought freely as if of himself, and spoke freely and acted freely as if of himself. And this is why the Lord does not teach man immediately, but mediately by means of the Word, and by means of doctrines and preachings from the Word, and by means of conversations and interaction with others; for from these things man thinks freely as if of himself.

[5] In no other way can man be saved. This follows both from what has been said about the laws of the Divine providence and also from this, that thoughts do not produce affections in man. For if man knew all things of the Word, and all things of doctrine, even to the arcana of wisdom that the angels possess, and thought and spoke about them, so long as his affections were lusts of evil he could not be brought out of hell by the Lord. Evidently, then, if man were to be taught from heaven by an influx into his thoughts it would be like casting seed upon the way, or into water, or into snow, or into fire.