[2] It is comparatively like a tree, which appears before the eyes luxuriant with branches, leaves, and fruits. All these are effects, but if you could examine a branch within as to the filaments, or a leaf as to fibers, or the fruit as to each and all things of it which are invisible, and the seed as to its invisible parts, of which the tree with all its members consists, you would see how innumerable and indescribable things lie hidden from the eyes. Once a flower was opened before the angels as to its interiors, which are called spiritual, and when they saw they said that there was within as it were a whole paradise, consisting of indescribable things.

[3] It is also like the human body with all its members and organs that appear before the eye, as compared with its interiors, where are so many organic forms, by pure arcana of all the sciences making so many bodies from one, even so that you might say that into it are gathered arcana of all the sciences, as Physics, Chemistry, Mechanics, Geometry, Acoustics, Optics, which arcana of the sciences can in no wise be explored, because not comprehended. Such is the internal with respect to the external, or the spiritual with respect to the natural, and the celestial with respect to the spiritual. The natural in itself regarded is nothing else than an external form, which is called the effect of spiritual things; and the spiritual is an external form, which is called the effect of celestial things; wherefore everything spiritual is from the celestial, and everything natural is from the spiritual. From this it is plain how it is to be understood that truth is the form of good, that good has its quality in truths, because form is in them, and without form quality is lacking; and that truth exists from good as from its own living cause; and that if you remove good from truths, it is as if you should take the kernel from an almond, the truth being like its shell; or as if you should take out the pulp from fruit, and leave only the skin. Hence truth without good is turned into what is fantastic, which appears externally like truth, but is empty within. So is the natural without the spiritual, and also the spiritual without the celestial.

[4] Because there are ineffable things in the spiritual which do not appear in the natural, and innumerable things in the celestial, therefore it is plain what is the nature of the natural, the spiritual, and the celestial, that they are ineffable with respect to one another. They follow after one another, as knowledge, intelligence, and wisdom; wherefore also men on earth, because they are in natural light, are called by the angels knowing, while angels of the Lord's spiritual kingdom are called intelligent; and angels of the Lord's celestial kingdom are called wise.

[5] The Word in the sense of the letter may be compared to a tree, surrounded with cortex or bark, entire, and endowed with vegetative life, and the spiritual sense may be compared to its nutrition from various juices and essences, partly ascending from the ground, partly imbibed from the air and ether, by means of the heat and light of the sun. If the sense of the letter alone existed, and not at the same time the spiritual sense and the celestial sense, the Word would be as a tree without sap, or as the bark alone without wood; but with those senses it is like a tree in its perfect state; indeed in a tree all the sap passes from the root through the bark or cortex, wherefore when that is taken away the tree dries up. Such would be the case with the spiritual sense of the Word without its natural sense.