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.

3196. 'And Isaac came out to meditate in the field' means a state of the Rational immersed in good. This is clear from the representation of 'Isaac' as the Divine Rational, often dealt with already, and from the meaning of 'meditating in the field' as its state when immersed in good. For 'meditating' is a state of the rational when this controls the mind. 'A field' however is doctrine and the things that constitute doctrine, 368, and so the things that constitute the Church as regards good, 2971. Consequently the expression of old 'meditating in the field' stands for thought immersed in good, which is the condition of an unmarried man (homo) with thoughts of a wife.