Fictitious and Symbolic Creatures in Art, by John Vinycomb, , at sacred-texts.com
The mediæval conception of the unicorn as the water-conner of the beasts was doubtless suggested by that belief of earlier ages which made the unicorn not merely symbolical of virtue and purity, but the more immediate emblem of Christ as the horn of our salvation (Psalms xcii. 10 and lxxxix. 17, 24), expressly receiving its general fulfilment in him (St. Luke i. 69). The horn, as an antidote to all poison, was also believed to be emblematical of the conquering or destruction of sin by the Messiah, and as such it appears in the catacombs at Rome. The unicorn is the companion of St. Justiana, as an emblem betokening in the beautiful legend her pure mind, resisting all the Geraldine-like dreams sent by magic art to haunt her, till she converted her tormentor himself.
He is remarkable, say the old writers, for his great strength, but more for his great and haughty mind, as he would rather die than be brought into subjection (Job xxxix. 10–12).
It was believed the only way to capture him was to leave a beautiful young virgin in the place where he resorted. When the animal perceived her, he would come and lie quietly down beside her, resting his head upon her lap, and fall asleep, when he would he surprised by the hunters who lay in wait to destroy him.
The unicorn is one of the most famous of all the chimerical monsters of antiquity. The Scriptures make repeated mention of such a creature, but of its shape we can form little conception. In Early Christian Art the unicorn symbolised the highest and purest virtue; not only was it one of the noblest bearings in the heraldry of the Middle Ages, but was
viewed as the immediate emblem of our Blessed Lord. Philippe de Thaun says in his "Bestiarius":
Whence comes the unicorn? It is older than the days of Job. Among the hieroglyphics of Ancient Egypt this wonderful creature is depicted. Sometimes
the body is that of an ass, sometimes that of a bull, sometimes that of a horse with the long twisted frontal horn for which he is noted. Is the myth derived from some mysterious single-horned antelope, as has been said, or is the one-horned rhinoceros the prototype of the legendary unicorn? As an emblem it figures on the obelisks of Nimroud and the catacombs of Rome. We read of this strange creature in Herodotus, and in Aristotle, who calls it the "wild ass"; Pliny calls it the "Indian ass," describing it as like a horse with a horn fixed in the front of his head. Cæsar counts it among the fauna of the Hyrcinian Forest. The earliest author who describes it is Ctesias (B.C. 400), who derives it from India. According to an Eastern legend the unicorn is found in Abyssinia. Lobo also describes it in his history of that country: there the animals are undisturbed by man, and live after their own laws. "Of the many ancient and famous men," says a modern writer, "who have written about the unicorn, no two seem to agree except when they copy from one another."
"Some writers" (says Guillim, p. 175) "have made doubt whether there be any such beast as this or no. But the great esteem of his horn (in many places to be seen) may take away that needless scruple."