7870. 'On that night' means their state - a state of evil. This is clear from the meaning of 'night' as a state when there is nothing but evil and falsity. For night describes the opposite of day and thick darkness the opposite of [clear] light, and 'day' and '[clear] light' mean a state in which truth and good reign. This being so, 'night' also means the last phase of the Church, for at that time falsities and evils reign because there is no faith or charity, see 2353, 6000. In addition 'night' means when vastation is completed, 7776, and also damnation, 7851. From all this it is evident that the state of those who are in hell is called 'night'. Not that the thick darkness of night envelops them, for they can see one another. But since the state of truth and good which exists in heaven is called 'day', the state of falsity and evil is called 'night'. Also thick darkness exists in hell when any light at all from heaven flows into it; for then the inferior light which they see by is reduced to nothing and becomes thick darkness.

[2] The source of the inferior light they see by is, it is true, light from the Lord coming through heaven; for in the next life no light comes from anywhere else. But among those in hell that light from Him enters by way of the ability to understand what is true. The ability enabling them to understand remains with them, as it does with every human being, however much they may be steeped in evil or falsity. But when that heavenly light passes on into their will - that is to say, into unwillingness to understand - and consequently passes into the evil and falsity that reside with them, the heavenly light is turned for them into inferior light resembling that emitted from a coal fire. And, as has been stated, that inferior light is converted into utterly thick darkness by the light of heaven when this flows into it. Regarding the inferior light in hell, its being like that emitted from a coal fire, see 1528, 3340, 4418, 4571; and regarding its conversion into thick darkness at the presence of the light of heaven, 1783, 3412, 4533, 5057, 5058, 6000. From all this it may be recognized that in the next life the kind of light each one has depends on whether his ability to understand is furnished with truths springing from good or with falsities arising from evil.