'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)

33. Everyone is capable of knowing very well that no life is possible without love of some kind, nor any type of joy whatsoever except the joy that flows out from the love. Furthermore the nature of the love determines the nature of the life and of the joy. If you took away your loves, and what amounts to the same, your desires (since these stem from love), thought would instantly perish and you would be as one dead. This I have been shown convincingly. Self-love and the love of the world present a semblance of life and of joy, but because they are absolutely contrary to true love, which is loving the Lord above all things and the neighbour as oneself, it is clear that neither of them is love but hatred. For the more anyone loves himself and the world, the more he hates his neighbour and so the Lord. Consequently true love is love to the Lord, true life is the life inherent in love from Him, and true joy is the joy of that life. The existence of more than one true love is not possible. Nor consequently is the existence of more than one true life possible which is the source of all true joy and happiness, such as angels in the heavens enjoy.