Ichthys

The ichthys, two intersecting arcs forming the outline of a fish, is among the earliest Christian symbols, in use by the second century and well before the cross became a common devotional sign. Its currency rests on a Greek acrostic: the letters of ichthys, fish, were read as Iesous Christos Theou Yios Soter, Jesus Christ, God's Son, Saviour. Because the confession is folded inside an ordinary word, the sign could circulate discreetly among Christians in the period before Constantine, though the familiar story that it served as a secret recognition token, one believer scratching an arc in the dust and a stranger completing it to prove their faith, is a later embellishment rather than documented ancient practice. The two clearest early attestations are the epitaph of Abercius, bishop of Hierapolis in Phrygia, composed before about 216 and rich in fish and eucharistic imagery, and the Licinia Amias inscription from Rome, of similar date, which pairs fish and anchor without naming Christ outright, evidence that the symbol was already doing devotional work that plain text could not risk doing openly.

A more elaborate variant, sometimes called the ichthys wheel, superimposes the five Greek letters radially into an eight-spoked figure; its best-known example, a marble slab from Ephesus, is widely presented as covert persecution-era signage, but the slab is generally dated to the Byzantine period, well after toleration, so it attests the acrostic's long afterlife rather than any early concealed use.

The fish resonated with the Gospels independently of the acrostic: the first disciples were fishermen whom Jesus called to be fishers of men, the feeding of the multitude multiplied loaves and fish, and the risen Christ shares a fish breakfast with the disciples on the shore. Tertullian, writing around the turn of the third century, punned that Christians, like little fish, are born in the water of baptism, following the great Fish, Christ himself, a play on words that only works because the acrostic reading was already common currency among his readers.

Fish imagery appears repeatedly in the Roman catacombs, cut into loculus slabs and painted beside eucharistic scenes of bread and wine, alongside the anchor and the Chi-Rho as one of a small vocabulary of signs that let belief be stated without a word. The plain cross displaced the fish as Christianity's dominant public emblem once toleration under Constantine removed the need for restraint, and the ichthys was largely dormant for well over a millennium. Its return, as a chrome car emblem and printed logo from the later twentieth century onward, is a self-consciously revivalist American evangelical fashion rather than a continuous practice, and it has spawned polemical replies, most famously the Darwin fish with added legs and the further rebuttals those in turn provoked, a modern exchange of bumper-sticker apologetics with no ancient counterpart.