Nicholas Cabasilas Chamaetos was born to a Thessalonican noble family, the nephew of the bishop Nilus Cabasilas, and was educated at Constantinople in classical rhetoric and philosophy. He served as advisor to the Emperor John VI Kantakouzenos during the political turmoil of the 1340s and 1350s, was a friend and theological ally of Gregory Palamas in the late phase of the Hesychast controversy, and entered religious life late in his life — probably never as a priest, certainly never as a bishop. He is one of the rare canonized lay theologians of the Eastern Church.
His two great works are the Life in Christ (Peri tis en Christo zois) — a seven-book treatise on baptism, chrism, and the Eucharist as the three sacraments that constitute the Christian life — and the Commentary on the Divine Liturgy, which became the standard Byzantine catechetical exposition of the Liturgy of St. John Chrysostom. The Life in Christ is the foundational text of Eastern lay sacramental theology: it presents the sacraments as not merely supplements to spiritual life but as the entire matter and form of Christian existence.
His theology was the great alternative to the monastic-ascetic emphasis of Palamas — not opposing it but completing it, by insisting that the union with God Palamas described as the goal of the hesychast monk was the same union offered in baptism and the Eucharist to every Christian. He died around 1392, probably as a monk on Mount Athos. His formal canonization was finally promulgated in 1983.