'A sandal tree' signifies aspects of the natural self.

(References: Apocalypse Explained 518)

506. And the third part of the trees was burnt up.- This signifies that the perceptions and knowledges of truth and good perished through desires springing from evil loves, as is plain from the signification of a third part, when used in reference to truths, for it denotes all, concerning which we shall treat in what follows; and from the signification of trees, as denoting the interior things of man, which are those of his mind (see above, n. 109), and thence the perceptions concerning truths and goods, and the cognitions of them (see above, n. 420); and from the signification of being burned, as denoting to perish by lusts springing from evil loves, as stated just above (n. 504), where it was shown that those lusts are signified by fire, wherefore to be burned denotes to perish by means of them.

[2] The third part signifies all, and therefore the third part of the trees the all of perception concerning truths and goods, and thence all the knowledges thereof, because three signifies what is full, the whole, and all, and these are said of truths; similarly, therefore, the third part, for third signifies the same as three. Numbers also multiplied into one another, and divided by one another, have a signification similar to the integers from which they are derived, as may be seen above (n.430:1). That the third part signifies all and is said of truths, may also be seen above (n. 384). The signification of third part in the following passages is similar:

"And the third part of the sea became blood (Verse 8)

"And the third part of the creatures which were in the sea, died" (Verse 9);

"A burning star fell upon the third part of the rivers" (Verse 10)

"And the third part of the waters became wormwood" (Verse 11);

"And the third part of the sun was smitten, and the third part of the moon, and the third part of the stars" (12; also chap. 9:15, 18; 12:4).

[3] Here, it is described how all perception of truth and good, and thence the cognition of them, would first perish by means of the loves of self and of the world, and the lusts and pleasures arising therefrom. The reason why the perception and cognition of spiritual truth and good perish through those loves and the lusts thence arising, is, that those loves are corporeal and merely natural loves, into which also man is born, and which, unless subdued and ruled by spiritual loves, which are out of heaven from the Lord, extinguish all perception and thence cognition concerning the truths and goods of heaven and of the church; for those loves, considered in themselves, are altogether opposite to spiritual loves. It is therefore evident, that when the church lapses, it first passes from an internal spiritual into a natural state, and this consists in the love of self and of the world above all things; consequently it then comes into thick darkness in regard to all things of heaven and of the church, although it may be in light as to the things of the world.

[4] When perception concerning spiritual truths and goods perishes, the cognition of them also perishes, for although man knows them, and speaks of them, either from the Word or from doctrine, still he does not know them, when he has no perception of them. The perception of a thing makes the cognition of it. Cognition without perception is not alive, but dead, and is also a cognition of the meaning of the words only, and not of the thing itself. Such are the cognitions of truth and good from the Word and the doctrine of the church with those in whom the love of self and the love of the world hold the chief place, although they have been taught to speak and preach artificially and ingeniously about them. They are only shells, which appear before the vulgar to have kernels within, although they are empty.