I thought it'd be interesting to have a thread on the 8th and 9th Ecumenical Councils. As I come across quotes and other relevant material I'm going to post it here, I invite everyone else to please do the same
"The hesychastic confict, as it was called, ended with the Councils which took place in Constantinople in 1341, 1346 and 1351. The Last Council, which 'justified' St. Gregory Palamas, proponent of the hesychastic life, is considered to be Ecumenical: 'We think that the Council of Constantinople in the time of Saint Gregory Palamas in 1351, judging at least on the basis of its great theological work, can be and deserves to be counted among the Ecumenical Councils of the Orthodox Church, to which it is in now way inferior as to the soteriological significance of its theology. This Council constitutes the proof of the continuing conciliarity of the Orthodox Church and of the living experience and theology concerning salvation in Christ' (Quoting: Athanasius Gievtits. Christ Beginning and End. p. 195. In Gk.)
...hesychasm [has] been 'justified' by the Council of Constantinople and consequently one who speaks against these things is no longer within the Orthodox tradition and at any rate creates preconditions for being cut off from its life." - Met. Hierotheos, Orthodox Psychotherapy: The Science of the Fathers, (Birth of the Theotokos Monastery, 1994), pp. 326-327, 330-331 (This quote can also be found online at this site)