Eagle

No animal has served as an emblem of state as continuously as the eagle, and the line of descent is traceable rather than accidental.

The aquila was the standard of the Roman legion, a silver or gold eagle on a pole carried by the aquilifer. The reform that made the eagle the sole legionary standard is attributed to Marius in 104 BCE. Loss of the aquila was the gravest disgrace a legion could suffer, and the recovery of the standards lost at Carrhae was presented by Augustus as a major achievement of his reign. The bird was the bird of Jupiter, so the standard carried a religious as well as a military charge.

From Rome the eagle passes forward directly. The Byzantine and then Holy Roman use of the double-headed eagle, looking east and west, was inherited by Russia after Moscow claimed the Byzantine succession, and by Austria. The single-headed eagle was taken by Napoleon in conscious imitation of Rome, by Prussia and then Germany, by Mexico from an entirely separate Mexica foundation story, and by the United States in the Great Seal of 1782, where the bald eagle holds arrows and an olive branch. Benjamin Franklin's letter disparaging the bald eagle as a bird of bad moral character is genuine, but it is a private joke in a letter to his daughter, not a proposal for the turkey, and the story is habitually mistold.

The eagle feather in many Indigenous North American nations is a different matter entirely, a sacred object with specific protocols governing who may hold one and how, protected in United States law by exemption from the Bald and Golden Eagle Protection Act for enrolled members of federally recognised tribes. It is not an emblem of state and should not be discussed as one.

The eagle is one of the four living creatures. Ezekiel 1:10 describes four faces on each creature, a man, a lion, an ox and an eagle, and Revelation 4:7 gives four separate creatures with those forms around the throne. The pairing of the four with the four gospels is a Christian development, and it is neither original nor uniform.

Irenaeus, writing around 180, is the earliest to make the analogy in Against Heresies 3.11.8, and his assignment is not the familiar one: he gives the lion to John, the ox to Luke, the man to Matthew and the eagle to Mark. Augustine offered another arrangement again, with the lion to Matthew and the man to Mark. The scheme that won is Victorinus of Pettau's, man to Matthew, lion to Mark, ox to Luke, eagle to John, which Jerome adopted, and which passed through Gregory the Great and works like the Book of Kells into the standard Western iconography.

The reasoning for the eagle and John is that his gospel opens in heaven rather than on earth, with the Word rather than a genealogy or a wilderness. The reasoning is retrospective in every case; the assignments were made to fit and then justified.

That there are at least three competing patristic schemes is worth stating, because the familiar arrangement is usually presented as though it were self-evident or apostolic. It is neither. It is a fourth-century editorial preference that succeeded.

Garuda, the eagle-like mount of Vishnu, is a separate tradition with no relation to any of this. He is the enemy of serpents, the vehicle on which Vishnu flies, and a state emblem of Indonesia and Thailand. The visual resemblance to Western imperial eagles is convergence: a large raptor is what a state reaches for when it wants to look formidable.