The ichthys or ichthus (//), from the Greek ikhthýs (ἰχθύς, "fish"), is a symbol consisting of two intersecting arcs, the ends of the right side extending beyond the meeting point so as to resemble the profile of a fish. It was used by early Christians as a secret Christian symbol and now known colloquially as the "sign of the fish" or the "Jesus fish".
Greeks, Romans, and many other pagans used the fish symbol before Christians. In pagan beliefs, Ichthys was the offspring of the ancient Sea goddess Atargatis, and was known in various mythic systems as Tirgata, Aphrodite, Pelagia, or Delphine. The word also meant "womb" and "dolphin" in some tongues. Before Christianity adopted the fish symbol, it was known by pagans as "the Great Mother", and "womb". Its link to fertility, birth, and the natural force of women was acknowledged also by the Celts, as well as pagan cultures throughout northern Europe. In certain non-Christian beliefs the fish also has been identified with reincarnation and the life force.
- Iota (i) is the first letter of Iēsous (Ἰησοῦς), Greek for "Jesus".
- Chi (ch) is the first letter of Christos (Χριστός), Greek for "anointed".
- Theta (th) is the first letter of Theou (Θεοῦ), Greek for "God's", the genitive case of Θεóς, Theos, Greek for "God".
- Upsilon (y) is the first letter of (h)uios (Υἱός), Greek for "Son".
- Sigma (s) is the first letter of sōtēr (Σωτήρ), Greek for "Savior".
This explanation is given among others by Augustine in his Civitate Dei, where he notes that the generating sentence " Ἰησοῦς Χριστὸς [sic] Θεοῦ Υἱὸς Σωτήρ" has 27 letters, i.e. 3 x 3 x 3, which in that age indicated power. (This suggestion is obviously spurious, resulting from Augustine's ignorance of Greek.)  Augustine quotes also an ancient text from the Sibylline oracles whose verses are an acrostic of the generating sentence.
A fourth century A.D. adaptation of ichthys as a wheel contains the letters ΙΧΘΥΣ superimposed such that the result resembles an eight-spoked wheel.
Fish in the Gospels
Having resurrected, Jesus is offered some grilled fish and honeycomb in Luke 24:41-43.
At the feeding of the five thousand, a boy is brought to Jesus with "five small loaves and two fish". The question is asked, "But what are they, among so many?" Jesus multiplies the loaves and fish to feed the multitude. In Matthew 13:47-50, the Parable of Drawing in the Net, Jesus compares God's decision on who will go to heaven or to hell ("the fiery furnace") at the end of this world to fishers sorting out their catch, keeping the good fish and throwing the bad fish away. In John 21:11, it is related that the disciples fished all night but caught nothing. Jesus instructed them to cast the nets on the other side of the boat, and they drew in 153 fish. In Matthew 17:24-27, upon being asked if his Teacher pays the temple (or two-drachma) tax, Simon Peter answers yes. Christ tells Peter to go to the water and cast a line, saying that a coin sufficient for both of them will be found in the fish's mouth. Peter does this and finds the coin.
The fish is also used by Jesus to describe "the Sign of Jonah". (Matthew 12:38-45) This is symbolic of the resurrection of Christ upon which the entire Christian faith is based. ( 1 Corinthians 15:1-58)
According to tradition, ancient Christians, during their persecution by the Roman Empire in the first few centuries after Christ, used the fish symbol to mark meeting places and tombs, or to distinguish friends from foes:
According to one ancient story, when a Christian met a stranger in the road, the Christian sometimes drew one arc of the simple fish outline in the dirt. If the stranger drew the other arc, both believers knew they were in good company. Current bumper-sticker and business-card uses of the fish hearken back to this practice.— Christianity Today, Elesha Coffman, "Ask The Expert"
There are several other hypotheses as to why the fish was chosen. Some sources indicate that the earliest literary references came from the recommendation of Clement of Alexandria to his readers (Paedagogus, III, xi) to engrave their seals with the dove or fish. However, it can be inferred from Roman monumental sources such as the Cappella Greca and the Sacrament Chapels of the catacomb of St. Callistus that the fish symbol was known to Christians much earlier. Another probable explanation is that it is a reference to the scripture in which Jesus miraculously feeds 5,000 people with fish and bread (Matthew 14:15-21, Mark 6:30-44, Luke 9:12-17, and John 6:4-13). The ichthys may also relate to Jesus or his disciples as "fishers of men" (e.g., Mark 1:17). Tertullian, in his treatise On Baptism, makes a pun on the word, writing that "we, little fishes, after the example of our ΙΧΘΥΣ Jesus Christ, are born in water." Still another explanation could be the reference to the sign of Jonah. Just like he was in the belly of a big fish, so Christ was crucified, entombed for three days, and then rose from the dead.
Revival and adaptations of the symbol
In the 1970s the "Jesus Fish" started to be used as an icon of modern Christianity. In 1973 the symbol and message was taken to the Aquarius Rock Festival in Nimbin, Australia. Today, it can be seen as a decal or emblem on the rear of automobiles or as pendants or necklaces as a sign that the owner is a Christian. Versions of this include an Ichthys with "Jesus" or "ΙΧΘΥΣ" in the centre, or simply the Ichthys outline by itself.
- "ichthus". Oxford English Dictionary (third ed.). 2007.
- Elesha Coffman (August 8, 2008). "What is the origin of the Christian fish symbol?". Christianity Today.
- "Evolution of religious bigotry"
- Christian H. Bull, Liv Ingeborg Lied, John D. Turner, editors (2012). Mystery and Secrecy in the Nag Hammadi Collection and Other Ancient Literature: Ideas and Practices. Leiden, The Netherlands: Koninklijke Brill NV. p. 327. ISBN 978-90-04-21207-7.
- The initial "h" was sometimes pronounced, depending on dialect and period, but in Ionic orthography the sound was written with the rough breathing diacritical mark instead of a full letter, and so would not be used to form an acronym)
- This article incorporates text from a publication now in the public domain: Augustine. The City of God. Wikisource. XVIII, 23.
- Bagatti, Bellarmino (1984). The church from the circumcision: history and archaeology of the Judaeo-Christians. Studium Biblicum Franciscanum, Collectio Minor, n.2. Jerusalem. p. 215.
- Sibylline oracles, Book viii, 284-330 (Greek text, 217-250)
- Christian H. Bull, Liv Ingeborg Lied, John D. Turner, editors (2012). Mystery and Secrecy in the Nag Hammadi Collection and Other Ancient Literature: Ideas and Practices. Leiden, The Netherlands: Koninklijke Brill NV. pp. 340, 343. ISBN 978-90-04-21207-7.
- "Symbolism of the Fish". Catholic Encyclopedia. New York: Robert Appleton Company. 1913.
- http://ccel.org/fathers2/ANF-03/anf03-49.htm#P11466_3245563 §1
- "Christian symbols: Fish (Ichthus), cross and crucifix". religioustolerance.org. Retrieved 22 April 2014.
The body of the symbol may be empty, or may contain a name ('Jesus' or 'ICTUS').
- See, Robison, Greg, Christian Rock Festivals,(New York: The Rosen Publishing Co., 2009), p.7 https://books.google.com/books?id=0w7vTv6hzIMC&pg=PA7&lpg=PA7&dq=ichthus+christian+music+festival&source=bl&ots=oTf0y7CPi1&sig=D5FLBuNRRDLUKKPCIk6Qik55D5s&hl=en&ei=gkDuSrCMDdSztgf3qtk6&sa=X&oi=book_result&ct=result&resnum=8&ved=0CBsQ6AEwBzgK#v=onepage&q=ichthus%20christian%20music%20festival&f=false
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- Coins of the Emperor Augustus
- Coins of the Emperor Domitian
- earlychristians.org on early Christians in general including martyrdom
- Ichthus Christian Fellowship A large Christian organisation in the UK led by Roger Forster
- Ichthus Music Festival The longest running Christian music festival in the nation having been started in 1970 as a Christian response to Woodstock.
- Principal Christian Symbols: The Fish (Ichthus), Cross & Crucifix Extensive explanations on several popular Christian symbols, including the ichthys
- Symbolism of the Fish - Catholic Encyclopedia article
- The Harvard Ichthus, Journal of Christian Thought