512. And the third part of the sea became blood.- That this signifies, that everything therein became the falsity of evil, is evident from the signification of the third part, which denotes all (see above, n. 506); and from the signification of the sea, which denotes the natural man, as explained above (n. 511); the third part of the sea therefore signifies the whole natural man, and everything therein; and from the signification of blood, which denotes the falsity of evil, concerning which also above (n. 329:2). From these things the spiritual sense of this verse can be seen, namely, that the great mountain burning with fire cast into the sea, and the third part of the sea becoming blood, signifies that the love of self, when it enters and occupies the natural man, turns every scientific therein into the falsity of evil.

[2] The love of self is merely a corporeal love, springing up from the ebullition and fermentation of effete substances, and from the irritant action of these inwardly in the body, whence the perceptive [faculty] of the mind, which requires a pure atmosphere, not only grows dull and gross, but also perishes. That the love of self is from that origin, is evident from its correspondence with human excrement. For those who have been allured by this love, in the other life, love foul smelling filth above all other things, and the stench of it is grateful to them, which is a sign that the effluvium arising therefrom affects the sensory of their smell with delight, as it before affected the common sensory, which is extended on all sides by means of interior cuticles. From this fact alone it is evident, that the love of self is gross and sordidly corporeal above all loves, and, consequently, that it takes away all spiritual perception which pertains to the truth and good of heaven and the church; it also closes the spiritual mind, and fixes its abode entirely in the natural and sensual man, which communicates most intimately with the body, and not at all with heaven. It therefore comes to pass, that all those in whom the love of self rules are sensual, and see the things which pertain to heaven and the church, only in thick darkness; and when they are alone and think in themselves, they reject and deny them. The signification of the third part of the sea being turned into blood, because the great mountain burning with fire was cast into it, is now evident from these things.

The sun in the Bible represents the Lord, with its heat representing His love and its light representing His wisdom. “Daytime,” then, represents a state in which we are turned toward the Lord, receiving His love and being enlightened by His truth. And “nighttime,” obviously, represents states in which we are turned away from the Lord, left cold and blind to the truth. The most common word used for it in the New Christian theology is “obscurity.” The darkness is not absolute, of course. The light of the moon represents the understanding we can have based on facts and our own intelligence. But while the moon reflects some of the sun's light, it offers almost no heat, so this kind of understanding is a cold one, without the warmth of love. And at its darkest and coldest, night represents a state of judgment. This happens when a person -- or a church -- becomes so mired in evil and falsity that there is no light or heat. The Lord can then step in, separate the good from the evil, consign the evil to hell and begin rebuilding based on the remnant that is still good. Drastic as that sounds, it is something that we all go through repeatedly in various aspects of our loves, so that we can be rid of what is evil and let the Lord rebuild us as angels.