'Grass' is natural truth, and 'flower of the field' is spiritual truth, as in Isaiah 40:5, 6. Green grass, in the Word, signifies the good and truth of the church, and of faith, which first springs up in the natural man. This is also signified by 'herb in the field.' Grass and the pulse of the herb, as in Psalm 32:2, signify what is most vile. Grass signifies science from a spiritual origin, or that by which spiritual truth is confirmed. 'Reeds and rushes' signify science from a sensory origin, or the things which confirm the fallacies of the senses, as in Isaiah 25:7. This science, considered in itself, is only a part of the lowest natural degree, which may be justly called material and bodily, in which there is little or no life. Green grass also signifies that which is alive with man. 'Grass burnt up' signifies the things which are dead in him. Grass signifies the scientific principle. Just as green grass serves animals for support, spiritual truth serves men for spiritual nourishment.

(References: Apocalypse Explained 507)

In the Word, “light” in the highest sense represents Divine Truth: knowledge, ideas, understanding that come to us from the Lord. In lesser degrees -- the light of a lamp, the light of the moon and so forth -- it represents lower levels of truth, ideas and understanding drawn from more earthly sources. Also, the sun in the Word represents the Lord, with its heat representing the divine love and its light representing the divine wisdom. That wisdom flows into our minds and enters our lives in the form of truth -- things we can know and ponder that lead us and help us to be good people. This connection between light and thought is one of many spiritual/natural relationships that's embedded in our common language. People “see the light” when they understand something; we try to “shed some light” by bringing new thoughts to a difficult question; people are “enlightened” when they get new information or a more complete understanding of something. And a light bulb in a cartoon represents an idea!