ACEMETI. - That is, the "sleepless ones" (ἀκούμητοι): ascetics so called because, divided into various shifts, they alternated uninterruptedly in the recitation of the liturgical prayers. They were instituted by St. Alexander the Acoemete, of Constantinople. They resided first at the Irenaion (today Cibukli) on the Asian coast of the Bosphorus, then at Constantinople in the monastery of Studios.
The most illustrious of them was St. Marcellus, a disciple of Alexander. The A. played an effective part in the theological controversies of the 5th and 6th centuries, as defenders of orthodoxy especially against the emperor Anastasius and the empress Theodora.
It was in fact the A. who denounced to Pope Felix III the patriarch Acacius, who had dared to read the name of the Monophysite Peter Mongus on the diptychs, during the liturgy at which the pontifical legates were also present, and who were for this reason excommunicated by the Pope, who deposed the patriarch (484).
Another occasion to defend orthodoxy presented itself to the A. when certain monks of Lesser Scythia (today Dobruja) proposed at Constantinople (519) the formula "One of the Trinity has suffered in the flesh," orthodox in itself, and which according to them should have reconciled the Tome of Leo and the anathemas of Cyril. The formula, however, aroused the suspicion of the A., who attacked the Scythian monks; these went to Rome to set out their ideas to Pope Hormisdas. After fourteen months (June 519-62, 520) of their not untroubled stay in Rome, he sent them back to the East, declaring, in a letter to the emperor Justinian and to the patriarch Epiphanius, that the christological formula they championed was superfluous in comparison with that adopted by the Council of Chalcedon.
The anti-Monophysite position of the A. ended by driving them toward the Nestorian heresy, inasmuch as, in order to vindicate the two natures, divine and human, in Christ, they went so far as to veil the divine character of his single Person; which they did implicitly by denying, like the Nestorians, to the Virgin the title of Mother of God (Θεοτόκος). Pope John II, at the formal request of Justinian, pronounced against them a sentence of condemnation (24 March 534).
After this time the A. disappear from history. They were succeeded in the monastery of Studios and in the reform of monastic life by the Studite monks under the guidance of the hegumen St. Theodore.