358. I. ZEAL, CONSIDERED IN ITSELF, IS LIKE THE ARDENT FIRE OF LOVE, What jealousy is cannot be known, unless it be known what zeal is; for jealousy is the zeal of conjugial love. The reason why zeal is like the ardent fire of love is, because zeal is of love, which is spiritual heat, and this in its origin is like fire. In regard to the first position, it is well known that zeal is of love: nothing else is meant by being zealous, and acting from zeal, than acting from the force of love: but since when it exists, it appears not as love, but as unfriendly and hostile, offended at and fighting against him who hurts the love, therefore it may also be called the defender and protector of love; for all love is of such a nature that it bursts into indignation and anger, yea into fury, whenever it is disturbed in its delights: therefore if a love, especially the ruling love, be touched, there ensues an emotion of the mind; and if it be hurt, there ensues wrath. From these considerations it may be seen, that zeal is not the highest degree of the love, but that it is ardent love. The love of one, and the correspondent love of another, are like two confederates; but when the love of one rises up against the love of another, they become like enemies; because love is the esse of a man's life; therefore he that assaults the love, assaults the life itself; and in such case there ensues a state of wrath against the assailant, like the state of every man whose life is attempted by another. Such wrath is attendant on every love, even that which is most pacific, as is very manifest in the case of hens, geese, and birds of every kind; which, without any fear, rise against and fly at those who injure their young, or rob them of their meat. That some beasts are seized with anger, and wild beasts with fury, if their young are attacked, or their prey taken from them, is well known. The reason why love is said to burn like fire is, because love is spiritual heat, originating in the fire of the angelic sun, which is pure love. That love is heat as it were from fire, evidently appears from the heat of living bodies, which is from no other source than from their love; also from the circumstance that men grow warm and are inflamed according to the exaltation of their love. From these considerations it is manifest, that zeal is like the ardent fire of love.
359. II. THE BURNING OR FLAME OF THAT LOVE, WHICH IS ZEAL, IS A SPIRITUAL BURNING OR FLAME, ARISING FROM AN INFESTATION AND ASSAULT OF THE LOVE. That zeal is a spiritual burning or flame, is evident from what has been said above. As love in the spiritual world is heat arising from the sun of that world, therefore also love at a distance appears there as flame: it is thus that celestial love appears with the angels of heaven; and thus also infernal love appears with the spirits of hell: but it is to be observed, that that flame does not burn like the flame of the natural world. The reason why zeal arises from an assault of the love is, because love is the heat of every one's life; wherefore when the life's love is assaulted, the life's heat kindles itself, resists, and bursts forth against the assailant, and acts as an enemy by virtue of its own strength and ability, which is like flame bursting from a fire upon him who stirs it: that it is like fire, appears from the sparkling of the eyes from the face being inflamed, also from the tone of the voice and the gestures. This is the effect of love, as being the heat of life, to prevent its extinction, and with it the extinction of all cheerfulness, vivacity, and perceptibility of delight, grounded in its own love.
360. It may be expedient here to show how the love by being assaulted is inflamed and kindled into zeal, like fire into flame. Love resides in a man's will; nevertheless it is not inflamed in the will itself, but in the understanding; for in the will it is like fire, and in the understanding like flame. Love in the will knows nothing about itself, because there it is not sensible of anything relating to itself, neither does it there act from itself; but this is done in the understanding and its thought: when therefore the will is assaulted, it provokes itself to anger in the understanding, which is effected by various reasonings. These reasonings are like pieces of wood, which the fire inflames, and which thence burn: they are therefore like so much fuel, or so many combustible matters which give occasion to that spiritual flame, which is very variable.
361. We will here unfold the true reason why a man becomes inflamed in consequence of an assault of his love. The human form in its inmost principles is from creation a form of love and wisdom. In man there are all the affections of love, and thence all the perceptions of wisdom, compounded in the most perfect order, so as to make together what is unanimous, and thereby a one. Those affections and perceptions are rendered substantial; for substances are their subjects. Since therefore the human form is compounded of these, it is evident that, if the love is assaulted, this universal form also, with everything therein, is assaulted at the same instant, or together with it. And as the desire to continue in its form is implanted from creation in all living things, therefore this principle operates in every general compound by derivation from the singulars of which it is compounded, and in the singulars by derivation from the general compound: hence when the love is assaulted, it defends itself by its understanding, and the understanding (defends itself) by rational and imaginative principles, whereby it represents to itself the event; especially by such as act in unity with the love which is assaulted: and unless this was the case the above form would wholly fall to pieces, in consequence of the privation of that love. Hence then it is that love, in order to resist assaults, hardens the substance of its form, and sets them erect, as it were in crests, like so many sharp prickles, that is, crisps itself; such is the provoking of love which is called zeal: wherefore if there is no opportunity of resistance, there arise anxiety and grief, because it foresees the extinction of interior life with its delights. But on the other hand, if the love is favored and cherished, the above form unbends, softens, and dilates itself; and the substances of the form become gentle, mild, meek, and alluring.
362. III. THE QUALITY OF A MAN'S ZEAL IS ACCORDING TO THE QUALITY OF HIS LOVE; THUS IT DIFFERS ACCORDING AS THE LOVE IS GOOD OR EVIL. Since zeal is of love, it follows that its quality is such as the quality of the love is; and as there are in general two loves, the love of what is good and thence of what is true, and the love of what is evil and thence of what is false, hence in general there is a zeal in favor of what is good and thence of what is true, and in favor of what is evil and thence of what is false. But it is to be noted, that of each love there is an infinite variety. This is very manifest from the angels of heaven and the spirits of hell; both of whom in the spiritual world are the forms of their respective love; and yet there is not one angel of heaven absolutely like another as to face, speech, gait, gesture, and manner; nor any spirit of hell; yea neither can there be to eternity, howsoever they be multiplied into myriads of myriads. Hence it is evident, that there is an infinite variety of loves, because there is of their forms. The case is the same with zeal, as being of the love; the zeal of one cannot be absolutely like or the same with the zeal of another. In general there are the zeal of a good and the zeal of an evil love.