Fifth Council of Constantinople is a name given to a series of six patriarchal councils held in the Byzantine capital Constantinople between 1341 and 1351, to deal with a dispute concerning the mystical doctrine of Hesychasm. These are referred to also as the Hesychast councils or the Palamite councils, since they discussed the theology of Gregory Palamas, whom Barlaam of Seminara opposed in the first of the series, and others in the succeeding five councils. The result of these councils is accepted as having the authority of an ecumenical council by Orthodox Christians who sometimes call it the Ninth Ecumenical Council. Principal supporters of the view that this series of councils comprises the Ninth Ecumenical Council include Metropolitan Hierotheos (Vlachos) of Nafpaktos, Fr. John S. Romanides, and Fr. George Metallinos.
As it became clear that the dispute between Barlaam and Palamas was irreconcilable and would require the judgment of an episcopal council. A series of six patriarchal councils was held in Constantinople on 10 June 1341, August 1341, 4 November 1344, 1 February 1347, 8 February 1347, and 28 May 1351 to consider the issues. Collectively, these councils are accepted as having ecumenical status by Orthodox Christians, some of whom call them the Fifth Council of Constantinople and the Ninth Ecumenical Council.
The dispute over Hesychasm came before a synod held at Constantinople in May 1341 and presided over by the emperor Andronicus III Palaeologus. The assembly, influenced by the veneration in which the writings of Pseudo-Dionysius were held in the Eastern Church, condemned Barlaam, who recanted.
Barlaam's primary supporter Emperor Andronicus III died just five days after the synod ended. Although Barlaam initially hoped for a second chance to present his case against Palamas, he soon realised the futility of pursuing his cause, and left for Calabria where he converted to the Roman Church and was appointed Bishop of Gerace.
After Barlaam's departure, Gregory Akindynos became the chief critic of Palamas. A second council held in Constantinople in August 1341 condemned Akindynos and affirmed to findings of the earlier council. Akindynos and his supporters gained a brief victory at the third synod held in 1344 which excommunicated Palamas and one of his disciples, Isidore Buchiras. Palamas and Buchiras recanted.
In 1347, however, after a vicious civil war, their protector, John Cantacuzenus, entered Constantinople and forced his opponents to crown him co-emperor. In February 1347, a fourth synod was held which deposed the patriarch, John XIV, and excommunicated Akindynos. Isidore Buchiras, who had been excommunicated by the third synod, was now made patriarch. In the same month, the Barlaamite party held a competing synod which refused to acknowledge Isidore and excommunicated Palamas. Akindynos having died in 1348, Nicephorus Gregoras became the chief opponent of Hesychasm.
In May 1351, a patriarchal council conclusively exonerated Palamas and condemned his opponents. This synod ordered that the metropolitans of Ephesus and Ganos be defrocked and jailed. All those who were unwilling to submit to the orthodox view were to be excommunicated and kept under surveillance at their residences. A series of anathemas were pronounced against Barlaam, Akindynos and their followers; at the same time, a series of acclamations were also declared in favor of Gregory Palamas and the adherents of his doctrine.
Gregoras refused to submit to the dictates of the synod and was effectively imprisoned in a monastery until the Palaeologi triumphed in 1354 and deposed Cantacuzenus.