'A raven,' as in Genesis 8:7, signifies falsities. The spiritual self only knows general truths from the Word, and forms its conscience from these, and the general truths of the Word are accommodated to the fallacies of the senses. So countless falsities attach themselves, and insinuate themselves into those general truths, and they cannot be drawn out. These falsities are what 'the raven which went forth in going and returning' signifies. 'Sons of the raven,' as in Psalm 147:8, 9, signify natural people in a dim light arising from fallacies relating to divine truth.

(References: Arcana Coelestia 865)

585. That 'the evil of man had been increased on the earth' means that the will for good started to go out of existence is clear from what has been stated before about no will existing any longer, but only evil desire, and also from the meaning of 'man on the earth'. In the literal sense 'the earth' is where mankind is, in the internal sense, where love is. And because love consists either in the will or else in evil desire, 'the earth' stands for man's will itself. In fact it is from willing rather than from knowing and understanding that a person is human, for knowing and understanding flow from his willing. Anything that does not flow from his willing, he does not wish to know or to understand. Indeed when he says or does something other than what the wills there is still something of the will, remote from speech and action, which governs him. That the land of Canaan, or the Holy Land, stands for love and so for the will of the celestial man may be confirmed from many places in the Word; and in like manner that the lands of various nations stand for their loves, which taken in general are self-love and love of the world. But as this point occurs so frequently there is no need to delay over it here. From these considerations it is clear that 'the evil of man on the earth' means his natural evil, which resides in the will, and which is said to have 'increased', because that natural evil had not become so bad with every one - though their intentions were selfish - that they did not wish good to others. 'The imagination of the thoughts of his heart' however means that such perversity became complete.