Greek philosopher and lay theologian. A native of Alexandria, he studied under the Neoplatonist philosopher Ammonius (of whose works he was an editor). The epithet philoponos, ‘lover of labour’, was probably given him in view of his industriousness. As a philosopher John has been described as one of the most original thinkers of his time, notable especially for his criticism of the prevailing Aristotelian doctrine of the eternity of the world. His writings prior to ca. 553 dealt with many different aspects of Aristotelian philosophy and survive only in Greek. It seems that it was the Council of Constantinople of 553 that led him to turn his attention to theology ( CPG 7260–7274, and Supplement); most of this is known only in Syriac translation. This applies in particular to his main surviving theological work, the Diaitētēs, or ‘Arbiter’, on the Union (in the incarnate Christ). His Tmemātā, or ‘Sections’ against the Councils of Chalcedon (451) and Constantinople (553) are summarized in Michael Rabo’s Chronicle (VIII.13). His work on the Creation of the World, dating from ca. 557–60, extant in Greek, was written against the views of Cosmas Indicopleustes, the friend of Patr. Aba I. His later theological works are known only in excerpts or from hostile sources: this applies in particular to his ‘On the Trinity’, where his rigorous application of logic led him to speak of the oneness of the Trinity as an abstraction. This position, held by a number of theologians, was condemned as tritheism, generating a considerable polemical literature (among which is Peter of Kallinikos’s work ‘Against Damian’). John’s theological teaching was explicitly condemned at the Council of Constantinople in 680, but his philosophical works remained influential, first in Arabic translation, and then in 16th-cent. Western Europe in Latin.