Tonsure is the practice of some Christian churches of cutting the hair from the scalp of clerics as a symbol of their renunciation of worldly fashion and esteem. There were three forms of tonsure known in the seventh and eighth centuries:
(1) The Oriental, which claimed the authority of St. Paul and consisted in shaving the whole head. This was observed by churches owing allegiance to Eastern Orthodoxy. Hence Theodore of Tarsus, who had acquired his learning in Byzantine Asia Minor and bore this tonsure, had to allow his hair to grow for four months before he could be tonsured after the Roman fashion, and then ordained Archbishop of Canterbury by Pope Vitalian in 668.
(2) The Celtic: this consisted in shaving the whole front of the head from ear to ear, the hair being allowed to hang down behind. The Roman party in Britain attributed the origin of this tonsure to Simon Magnus, though some traced it back to the swineherd of Loegaire , the Irish king who opposed St. Patrick. The fact that it was common to all of the Celts, both insular and continental, is a sufficient refutation of the latter view. Some practicers of Celtic Christianity claimed for this, as for their Easter practices, the authority of St. John. It is entirely plausible that the Celts were merely observing an older practice which had become obsolete elsewhere.
(3) The Roman: this consisted in shaving only the top of the head, so as to allow the hair to grow in the form of a crown. This is claimed to have originated with St. Peter, and was the practice of the Catholic church until obligatory tonsure was abolished in 1972.
Needless to say, these claimed origins are unhistorical; the early history of the tonsure is lost in obscurity. This practice is not improbably connected with the Roman idea that long hair is the mark of a freeman, while the shaven head marks the slave.
Based on Charles Plummer's essay, "Excusrsus on the Pascal Controversy and Tonsure" (in his edition of Bede's Opera Historica, 1898).
Today in Eastern Orthodoxy and in the Eastern Rites of the Catholic Church, there are three types of tonsure: baptismal, monastic, and clerical. It always consists of the cutting of four locks of hair in a cruciform pattern: at the front of head as the celebrant says "In the Name of the Father", at the back of head at the words "and the Son", and on either side of the head at the words "and the Holy Spirit". In all cases, the hair is allowed to grow back; the tonsure as such is not adopted as a hairstyle. Baptismal tonsure is performed during the rite of Holy Baptism as a first scrificial offering by the newly baptized. Monastic tonsure (of which there are three grades: Rassophore, Stavrophore and the Great Schema ) is the rite of initiation into the monastic state. Clerical tonsure is done prior to ordination to the rank of reader. This has lead to the common usage that one is "tonsured a reader", althought technically the rite of tonsure occures prior to the actual ordination by laying on of hands.
In the "Latin" or Western Rite of the Roman Catholic Church, tonsure referred to the rite of inducting a person into the clergy. Once a seminarian received the tonsure, which for most consisted of a symbolic cutting of a few tufts of hair or at most a small bald spot toward the back of the had, he was officially considered a cleric, and in medieval times obtained the civil benefits of clerics. He could then also receive the minor orders which were prerequisites to the major orders. Today, though, one becomes a cleric only when one is ordained deacon. Paul VI adopted this rule in 1972 while simultaneously suppressing obligatory tonsure, the minor orders, and the subdiaconate. It is still maintained, however, by some monastic orders, including the Carthusians and Trappists, who have traditionally employed a very full version of tonsure.