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.

3498. 'I do not know the day of my death' means the life within the natural. This is clear from the meaning of 'day' as state, dealt with in 23, 487, 488, 493, 893, 2788, and from the meaning of 'death' as rising again or awakening into life, dealt with in 3326. 'The day of death' accordingly means a state of awakening to life, or what amounts to the same, it means life - the life within the natural, it is evident, being meant in particular here, because that life is the subject here. What is implied in all this does not become clear unless one knows about the life of the rational, and the life of the natural, or what amounts to the same, about the life of the internal man and the life of the external man. The life of the rational or internal man is distinct and separate from that of the natural or external man, so distinct indeed that the life of the rational or internal man may exist quite independently of the life of the natural or external man; but the life of the natural or external man cannot exist apart from that of the rational or internal man. For the external man lives from the internal man, so much so that if the life of the internal man ceased to be, the life of the external man would instantly be no more. Exterior things are accordingly dependent on interior in the way that things which are posterior exist from those that are prior, or as an effect exists from its efficient cause. For if the efficient cause ceased to be, the effect would instantly be no more. The same is also so with the life of the external man in relation to the life of the internal man.

[2] This may be seen even more clearly in the human being, for while a person is in the world, that is, while he lives in the body, his rational is distinct and separate from the natural, so much so that he can be raised above the level of external sensory perceptions which belong to the body, and even to a certain extent above the level of inner sensory perceptions which belong to his natural man, and to be aware on the level of his rational, and so of spiritual thought. This is even more evident from the fact that when a person dies he leaves behind him altogether the external sensory perceptions that belong to the body, retaining at the same time the life of his interior man. Indeed he brings with him even the facts that exist in the external or natural memory, though he does not have the use of them, see 2475-2477, 2479-2483, 2485, 2486. From this it is evident that the rational or internal man is distinct and separate from the external man. But while a person is living in the body his rational does not seem to be distinct and separate from the natural, the reason being that he is living in the world or the natural order. That being so the life of the rational manifests itself within the natural, so much so that the rational does not seem to have any life at all if the natural does not at the same time have any. The amount of life that the rational seems to have in this case depends on how far the natural corresponds to it - see above in 3493. From this it may be seen that there is a corresponding life in the natural, which life is meant by the words which Isaac addressed to Esau, 'I do not know the day of my death'. For 'Isaac' represents the rational, and 'Esau' the natural, in both cases as regards good.