37. As for the statement that 'the lights will be for signs, and for set times, and for days, and for years', this contains more arcana than can be presented at this point, though no arcanum at all is visible in the sense of the letter. For now only this can be said: Change in spiritual and celestial things takes place both on general and on particular scales, and is comparable to changes that take place through the day and through the year. Changes through the day are from morning to midday, from then on to evening, and through the night to the morning. Changes in the year similar, from spring to summer, from then on to autumn, and through winter to spring. These bring changes in temperature and amount of daylight, and so in the fertility of the earth. Compared to such changes are the changes that take place in spiritual and celestial things. Life without changes and variations would lead to sameness, and so no life at all. Good and truth would not be recognized and identified, let alone perceived. In the Prophets such changes are called 'ordinances', as in Jeremiah,

[Thus] said Jehovah who gives the sun for light by day and the ordinances of the moon and of the stars for light by night, These ordinances will not depart from before Me. Jeremiah 31:35-36.

And in the same prophet,

Thus said Jehovah, If I have not established My covenant of day and night, the ordinances of heaven and earth . . . Jeremiah 33:25.

But these things will in the Lord's Divine mercy be dealt with at Genesis 8:12.

5092. 'Each his dream in one night' means regarding what the outcome would be, which to them lay in obscurity. This is clear from the meaning of 'a dream' as foresight and consequent foretelling - and because a foretelling is meant, so also is the outcome, it being the outcome that is foretold; and from the meaning of 'night' as obscurity. In the spiritual sense 'night' means a state of shade brought about through falsity that is the product of evil, 1712, 2353, and so also obscurity, that is to say, mental obscurity. The obscurity belonging to night in the world is natural obscurity, but the obscurity belonging to night in the next life is spiritual obscurity. Natural obscurity comes about because the sun of the world is absent and the light received from it is lost, whereas spiritual obscurity comes about because heaven's sun, which is the Lord, is absent and the light, that is, intelligence received from it, is lost. This latter loss does not arise because the sun of heaven sets as the sun of the world does, but because a person or a spirit is living amid falsity that is the product of evil. He himself moves away from that sun and brings obscurity to himself.

[2] An idea simply of night and of the obscurity that comes with it is sufficient to enable one to see how the spiritual sense and the natural sense of something are related to each other. Furthermore there are three kinds of spiritual obscurity - the first being that which is due to falsity that is a product of evil; the second being that which is due to ignorance of the truth; and the third being the obscurity in which exterior things dwell, compared with interior ones, and so the obscurity in which ideas formed by the senses and present in the external man dwell, compared with the rational concepts present in the internal man. All three kinds of obscurity arise however because the light of heaven, or intelligence and wisdom flowing from the Lord, is not received. This light shines unceasingly, but falsity that is a product of evil either rejects, smothers, or else perverts it; ignorance of truth receives only a little; while ideas formed by the senses that are present in the external man reduce it to a dim light by making it a general or ordinary one.