It is obvious from what was said above that zeal is a spiritual blaze or flame. Since love in the spiritual world is heat arising from the sun there, love too looks there from a distance like a flame; and so does celestial love among the angels of heaven. So too does hellish love among the spirits of hell. But it should be known that this flame does not burn like a flame in the natural world.

[2] The reason why zeal arises from love being attacked is that love is the vital heat of every individual. When therefore his vital love is attacked, his vital heat catches fire and opposes it, and bursts out against the attacker. It behaves like an enemy employing his force and power, which is like a flame bursting out of a fire against anyone who stirs it up. Its resemblance to fire is clear from the eyes flashing, the face turning red, and from the tone of voice and from the gestures. Love, being vital heat, does this to prevent being extinguished, together with all the keenness, liveliness and the ability to feel pleasure which come from its love.