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.

Air" in the Bible represents thought, but in a very general way – our capacity to perceive ideas and the way we tend to think, rather than our specific ideas about specific things. We see the world around us through the air, and seeing corresponds to understanding. We hear through the air, and hearing corresponds to being taught and obeying. Birds fly in the air, and they represent specific thoughts and ideas. And breathing itself – taking in air and passing oxygen to the blood – represents our understanding of true spiritual ideas.

In Genesis 1:26, when used with fowls or birds of the air refers to the air we breathe, but sky, or heavens where are stars, and together these terms refer to both the spiritual and natural man, and to their food, or goods and truths. (Arcana Coelestia 57, 58)

In Genesis 3:8, the only Old Testament reference to air is in the phrase "cool of the day" (at the time of the evening breeze) which signifies the period when the church still had some spiritual perception. (Arcana Coelestia 221)

In Revelation 9:2; 16:17, air signifies the divine truth, darkened by infernal falsities. (Apocalypse Explained 541, Apocalypse Revealed 423)

In Revelation 16:17, everyone in the spiritual world breathes air according to his faith. (Apocalypse Revealed 708, Apocalypse Explained 1012, Apocalypse Revealed 708)