190 Comnena, Anna
usually accurate, without being excessively opinionated.
Although he served a king of absolutist tendencies, he
expressed a political philosophy in his Memoirestoward a
moderate government and a dialogue between king and
subjects. He died on October 18, 1511, at Argenton-
Château in France.
Further reading:Philippe de Commynes, The Mem-
oirs of Phillipe de Commynes,ed. Samuel Kinser and trans.
Isabelle Cazeaux, 2 vols. (Columbia: University of South
Carolina Press, 1969–1970); Philippe de Commynes: Mem-
oirs, The Reign of Louis XI, 1461–83,trans. Michael Jones
(Baltimore: Penguin Books, 1972).
Comnena, Anna SeeKOMNENE,ANNA.
companies SeeCONDOTTIERI, COMPANIES, AND
MERCENARIES.
compass, magnetic The medieval compass was a nav-
igational instrument, based on the use of a magnetized
needle, that, when suspended freely, pointed toward the
magnetic North and South Poles. It was suspended in
water or freely in the air. Of Chinese origin, such a com-
pass was adopted by Muslim sailors and became known
in western Europe in the 12th century. Its existence was
mentioned by Alexander Neckam (1157–1217) in his On
the Nature of Things.Physical and astronomical advances
in the 13th century produced a description of magnetic
qualities by Petrus Peregrinus (fl. 1261–69) of Maricourt
in 1269. During this period and until the end of the Mid-
dle Ages, the compass was used by sailors for navigation
and cartographers for map drawing.
Further reading:J. A. Bennett, The Divided Circle: A
History of Instruments for Astronomy, Navigation, and Sur-
veying(Oxford: Phaidon, Christie’s, 1987).
Compostela SeeSANTIAGO DECOMPOSTELA.
computus The medieval computus was an art and a
science that involved arithmetic to establish the church
CALENDAR, from the feast of EASTER, which was movable.
From the third century, the Christians reached an agree-
ment to celebrate Easter on the Sunday following the
Jewish Passover on 14 Nisan. However, there were dis-
agreements about the day when 14 Nisan fell. In 325, at
the council of NICAEA, the fathers invited all the
churches to celebrate Easter on the Sunday after the full
Moon after the spring equinox, or between March 22
and April 25. The possible variation was within five
weeks. The rules for calculating this were the object of
the computus.
See alsoABBO OFFLEURY;BEDE THEVENERABLE;HRA-
BANUSMAURUS;SYLVESTERII, POPE.
Further reading:Arno Borst, The Ordering of Time:
From the Ancient Computus to the Modern Computer,trans.
Andrew Winnard (Chicago: University of Chicago Press,
1993); Georges Declercq, Anno Domini: The Origins of the
Christian Era (Turnhout: Brepols, 2000); Charles
Williams Jones, Bede, the Schools, and the Computus,ed.
Wesley M. Stevens (Aldershot: Variorium, 1994); Regi-
nald Lane Poole, Studies in Chronology and History,ed.
Austin Lane Poole (1934; reprint, Oxford: Clarendon
Press, 1969).conciliarism and conciliar theory(conciliar move-
ment) Conciliarism was a body of doctrines devised to
improve and restore the government of the church and
especially to end the leadership vacuum created by the
Great SCHISM between 1378 and 1417, when there
were two then three competing popes. These ideas gave
a fundamental place to the calling of councils in the reg-
ular life of the church and make them permanent
instruments of reform of the ecclesiastical institutions
and clerical morals. In their most extreme form they
would have replaced the pope as the ultimate authority
for doctrine and discipline within the church. The rise
in importance of these conciliarist principles was linked
to the failure of all the bungling attempts to end the
Great Schism.
To end the animosity between the rival factions and
partisans of the two claimants to the papacy, scholars at
the University of Paris proposed as early as 1380 to
bypass the papacy’s power by referring to Christ’s inten-
tions for his whole church. If Christ had entrusted any
particular authority to Peter and his successors as the
bishops of Rome, he did so because he wanted the church
to have some source of ultimate authority and doctrinal
unity. The successors of Peter, the popes or bishops of
Rome, could not impede this fundamental law or concept
without betraying their mission.
The idea of a council representing the universality of
believers and called to restore the popes to the right path
became influential after 1400. Then a new generation of
theologians and canonists, such as Pierre d’AILLY, John
GERSON, and Francesco ZABARELLA, sought to put an end
to the scandalous divisions in the church by suggesting a
more elaborate ecclesiological doctrine. Most conciliarists
recognized the pope as the head of the church but were
opposed to his unlimited hegemony. Any supreme pontiff
was incomplete without the universal church behind him
and possessed no power that had not been delegated to
the whole or universal church. This led to the conclusion
that a council could judge and correct the pope. Councils
represented the whole church and held their authority
even more directly from Christ.
Following these ideas, the Council of CONSTANCE
proclaimed the deposition of Pope John XXIII (d. 1419)
and restored the unity of Christendom by electing a