The Cross of Life
The unique symbol of Celtic Christianity is the so-called Celtic cross, also known as the Cross of Iona, after the belief that Columba erected one at his monastery on the island. The connection with Columba, who represents the union of pagan and Christian spirituality in Ireland, is apt. The Celtic cross is said to be derived from the ancient Roman monogram of Christ, made from the combination of the Greek letters chi and rho, but this seems unlikely. The form of the cross, with its scooped-out arms and enclosing circle, is derived from an ancient form dating thousands of years before Christianity, an ancient symbol of the sun. The placement of the crosses at crossroads and marketplaces also echoes ancient custom, and some suppose this was done in conscious imitation of pagan monuments.
The Solar Calendar
The ancient Celtic solar calendar consisted of two solstices, two equinoxes, and four cross-quarter days marking the seasons. The four solar festivals, marked on a round representing the path of the year, form a solar cross, the basis of the Celtic cross.
As a spiritual symbol, the Ionic cross represents the coming together of earth and heaven — the crossroad of life and death joined with the eternal circle of heaven. From the pagan viewpoint, it can be seen as the joining of male and female symbolism. The four arms can also be seen to represent the zodiacal calendar important to early Christians — four cardinal directions, and the four fixed signs of the zodiac as represented by the evange-lists Matthew (and his emblem, the angel), Mark (the lion), Luke (the ox), and John (the eagle), with Christ represented by the center solar disk.