Commentaria in Isaiam
Where St. Augustine writes that the eagle renews itself by striking its hooked beak, which has grown so long that it cannot take food, against a rock: “Then it comes again to food, and all is restored: and after old age, like a young eagle, the vigor of all the limbs returns, the gleam of the plumage, the rudders of the feathers: it flies on high as before, a kind of resurrection takes place in it.” But another manner of this renewal, from Epicrates, Athenaeus and Albert the Great, is given by Aldrovandus, book 1 of his Ornithology, page 26: “They say,” he says, “that the aged eagle, at the time when the young are grown and can fly, if it finds a clear and wide fountain, is borne aloft above it to the third region of the air: where, when it has been warmed by the rays of the sun and the hot air, so that it seems almost burned up, it suddenly lowers and draws in its wings and glides down into the cold fountain, so that, the cold constricting it from outside, the heat is increased within: then, leaving the fountain, it flies to its nest not far off, and, covered by the wings of its young, dissolves in sweat, and so with its old feathers puts off old age and puts on new; and meanwhile, until they are grown, it is fed by the prey of its young. To this I have nothing to say, except that there are many marvels of nature. In two eagles that were kept among us I observed nothing of the kind; for they were ash-grey, and changed their plumage like other birds of prey.” Hence the proverb: “The eagle’s old age, the corydus’s youth”; the green and vigorous old age of some excels the sluggish youth of others. For the eagle excels the little bird corydus, even in its full age. Rightly says the Greek sage:
That old age is more pleasing which is like youth: that youth is more burdensome which is like old age:
So Cicero, book On Old Age: “Old age is honorable if it defends itself, if it keeps its right, if it is enslaved to no one, if it rules over its own to the last breath. For as I approve of a young man in whom there is something of the old, so I approve of an old man in whom there is something of the youth: he who follows this may be old in body, but never will be in mind,” and shows that Appius was such. Symbolically, then, the Saints are eagles. First, because they imitate the endowments and ways of eagles. The life and endowments of the eagle a poet embraces in these verses:
It flies on high, dwells in the rocks, wears down its beak, is king, and hunts, fasts, has a gem, the wheel of the sun alone tests its young, laps, renews its wings at the fountain, tawny, seeing its talons, cries out over fish and prey.
So the Saints ascend to heaven in mind: they dwell in the rock, that is, Christ: their curved beak, that is, the perversity of the soul, anger, rapacity, they wear down against the rock, that is, against the cross of Christ (note “wears down its beak”: for the aging eagle grows so large and hooked a beak that it cannot take food; whence Pliny, book 10, chapter 3, says that the eagle perishes not of old age but of hunger). Again, the Saints, like eagles, are kings of themselves and of the world, they hunt souls, they waste their bodies with fasting, they have the gem of grace and charity: by the gaze of the Sun of justice, that is, Christ, they test their young, that is, their children, whether they are true and genuine believers. For pious parents have no heart for their offspring unless these too cultivate piety and unless they conform themselves wholly to the precepts and nod of the divine Sun, according to the counsel of the Wise Man, Ecclesiasticus 16:1: “Rejoice not in ungodly children, if the fear of God be not with them.” Moreover, eagles, that is, the faithful Saints, do not drink deep, do not make themselves drunk, but lap and drink sober. If they grow old in vices, they renew themselves at the fountain of tears and penance. They are tawny, that is, magnanimous, like eagles and lions: for these are properly tawny. They look at their talons, that is, the lowliness of their nature, that they may humble themselves. Moreover, the eagle, when walking, draws in its talons, lest it wear down their edge, by which, says Plutarch, it warns us not to blunt the keenness of our wit on vile things, but to spend it on things arduous and excellent. Lastly, the eagle spies out its prey; and, snatching fish, that is, souls, from the devil, it cries out and rejoices.
Secondly, as the eagle is of a warm and dry temperament, and strong: so holy men are warm through zeal; through voluntary poverty, or also through abstinence, they are dry, and hence constant, and strong in adversity.
Thirdly, the eagle, as Aristotle, Aldrovandus and others testify, ordinarily lays only three eggs, of which the third, since two suffice to preserve the species, it casts out of the nest: so the Saints lay two eggs, namely the works of right reason and the works of grace; the third egg, namely the work of cupidities and carnal pleasures, they cast away: he, therefore, who is an eagle does not fasten to the ground a particle of the divine breath. Indeed Aristotle, from Musaeus, in the History of Animals, book 6, chapter 6, writes thus of the eagle: “It hatches two, it lays three (eggs), it rears one,” which, says Aldrovandus, though true for the most part, yet sometimes two young have been seen fed by it, sometimes three, as Avicenna and others report. Hence symbolically one young one signifies that the eagle, that is, a king, ought to leave the kingdom to one son, not to several: for monarchy is the best government, whence Homer, Iliad 2, 204: “It is not good to have the rule of many; let there be one lord.” Or, as the Latin poet has put it: The rule of many is always much confusion; many lords are a calamity; let there be one King alone.
Morally, one young one is to be reared by us: the work of charity and of the Holy Spirit. For the second young one, that is, works merely morally good and conformed to right reason, is to be left to the Gentiles and Philosophers: the Christian must work from faith and grace.
And Curtius Gonzaga has an emblem in which an eagle is so depicted that, under a stormy and lightning-lit sky, unharmed and untouched, gazing at the sun it seems to press from the other side toward a mountain; with this motto: “Neither can it kill me, nor can it terrify me.” It signifies a man who is frightened by no adversities from persevering in a love begun and in an honorable undertaking. For the bird denotes the man, the mountain virtue, the storm adversities. This is what Isaias says here: “They shall change strength, they shall take wings as eagles.”
Fourthly, eagles cannot hatch their eggs unless they bring an eaglestone (aetites) into the nest. The reason is that they themselves are so hot that the eggs are almost cooked (for they grow as hot as if they were boiling); wherefore it is necessary that the heat be tempered by the coolness of the aetites, and the laying hastened by its peculiar power. And since they bring into the nest only two small stones, namely a male and a female (as some hold), they also bring forth only two young. So Aldrovandus. So the Saints, in order to bring forth the works of the Spirit, need the aetites, that is, prudence and discretion, by which their zeal is tempered.
Fifthly, the noble and lofty eagle is a sign of a lofty and calm mind, which despises all earthly things. Hence the Egyptians, to signify one who scorns insults, painted an unmoved eagle, which threatened no harm with either wings or beak, and beside it a crow which provoked it and annoyed it with insults. The eagle, therefore, is a symbol of magnanimity, as may be seen in the emblem of Alciati, in which a noble eagle is depicted sitting on the tomb of the most valiant Aristomenes, with this inscription: