The word "Unitarian" historically refers to the oneness of God as opposed to the Trinity of God, belief in which is referred to as "Trinitarianism".
The word Trinity is not in the Bible, nor Unitarians hold, is the concept. The naming of Father Son and Holy Spirit hardly occurs, except as a echo of a baptismal formula. The doctrine dates from the early Middle Ages, as an effort to reconcile Jewish theology with Greek philosophy, and was adopted as doctrine at the Council of Nicea in 325 AD at the behest of Constantine. The leader of the Trinitarian position was St. Nicholas (later known as Santa Claus), who later actively persecuted Unitarians.
At that time the Unitarian position was called "Arianism" for its leader Arius of Alexandria. He and the idea were declared heretic, and was crushed except for a few remote Germanic tribes.
With the invention of the printing press in the 1450's, and the wide reading of the Bible, people discovered that the Trinity was not there, and Unitarians (often called Arians) sprang up all over Europe like crocus. In most places they were killed. Calvin burned the best known Renaissance Unitarian theologian, the Spaniard Servetus, in Geneva, in 1604. He was burned with a slow fire, taking half an hour to kill him, with his books and writings strapped to him. Earlier he had been burned in effigy by Catholics. (Servetus was also a doctor, and had discovered the pulmonary circulation of the blood.)
Many early Unitarians tended to be scientists or doctors, and serving the royal family sometimes led to acceptance. Krakow (the early capital of Poland), became one of the few places Unitarians were allowed to live without persecution. They formed a convocation in 1565. After the Counter Reformation began to gain strength, and they were less welcome in Krakow, they gathered from all over Europe in a town they settled near Krakow (Rakow), establishing a university and printing press, under the leadership of the Italian theologian Socinus.
Unitarian churches developed in Hungary and Transylvania, and were particularly free in areas controlled by Turkey. Francis David was influential among them, but his thought continued to evolve, out pacing that of some Unitarian thinkers. Sabbatarian Unitarianism developed, observing Jewish food laws and the Sabbath on the seventh day of the week.
With a change in the throne Unitarians in Poland had in 1660 to choose between death, becoming Catholic, or fleeing. Some survivors fled by wagon train to Transylvania, being robbed on their way through Hungary. Some Unitarians in Transylvania later become Jewish by way of Sabatariansim, since Jews were considered infidels rather than heretics, and were not being put to death....
source:
http://www.slc.bc.ca/mac/uni.htm
. I always enjoy this site (even as a Muslim)!
