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Portrait of The Council of Nicaea

General knowledge · Religion & belief

The Council of Nicaea

325 CE

Christianity — the first ecumenical council

The gathering of bishops summoned by the emperor Constantine in 325 to the town of Nicaea in Bithynia, now Iznik in north-western Turkey. It was the first council to claim to speak for the whole Church. It condemned the teaching of the Alexandrian priest Arius, who held that the Son was a creature; declared instead that the Son is homoousios, of one substance with the Father; issued a creed that is the ancestor of the one still recited; and settled a common method for dating Easter.

How to spot them

  • ▸Called by Constantine in 325; traditionally 318 bishops attended
  • ▸Arius and the slogan 'there was a time when he was not'
  • ▸Homoousios against homoiousios — the theological quarrel over a single letter
  • ▸First of the seven ecumenical councils recognised by both East and West

Key facts

An emperor summons three hundred or so bishops to a lakeside town in Bithynia, now Iznik (325)

Constantine I; the traditional figure is 318 bishops

The word homoousios, 'of one substance', inserted so that a single Greek letter could not blur the meaning

Homoousios against homoiousios, 'of like substance' — the iota that made the difference

An Alexandrian priest and his slogan 'there was a time when he was not' are condemned and exiled

Arius; Arianism survived him and dominated several later decades

It ruled that Easter should be kept on the same Sunday everywhere, and not by the Jewish calendar

The first Sunday after the first full moon on or after the spring equinox

A young deacon of Alexandria made his name there and spent five exiles defending its decision

Athanasius, later bishop of Alexandria — 'Athanasius contra mundum'

Its creed was enlarged at a council of 381 into the form recited at Mass today (381)

The Niceno-Constantinopolitan Creed; the filioque was added later in the West

A second council in the same town, in 787, ended the first iconoclast controversy (787)

The Second Council of Nicaea, seventh ecumenical council, restoring the veneration of icons

Twenty canons of discipline, including a ban on lending at interest by clergy

They also forbade kneeling on Sundays and in the Easter season

Key ideas

  • Constantine's motive was as much political as theological: a divided Church was a divided empire. He presided, paid for the bishops' travel and pushed for a form of words everyone could sign, without being a theologian himself.

Quick-fire facts

  • •Convened by the emperor Constantine I and opened in May 325 at Nicaea in Bithynia (modern Iznik, Turkey)
  • •Traditionally 318 bishops attended, a number chosen to echo Abraham's 318 servants in Genesis; the real figure was probably around 250 to 300
  • •It was the first ecumenical council, and the first of the seven accepted by both Catholic and Orthodox churches
  • •Arius taught that the Son was created and therefore not eternal; the council condemned him and he was exiled
  • •The key term homoousios, 'of the same substance', was contested against homoiousios, 'of like substance'
  • •The council fixed Easter as the first Sunday after the first full moon on or after the spring equinox, and detached it from the Jewish calendar
  • •It issued 20 canons on church discipline and recognised the precedence of Alexandria, Antioch and Rome
  • •Athanasius attended as a deacon and became the chief defender of its formula, suffering five exiles
  • •The creed used in liturgy today is more exactly the Niceno-Constantinopolitan Creed, expanded at Constantinople in 381
  • •A second council met at Nicaea in 787 and restored the veneration of icons; 2025 marked the 1,700th anniversary of the first

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Sources