Ancient heretics, who denied the duplicity of natures in Christ; thus denominated from Eutyches, the archimandrite or abbot of a monastery, at Constantinople, who began to propagate his opinion about A. D. 448. He did not, however, seem quite steady and consistent in his sentiments; for he appeared to allow of two natures, even before the union, which was apparently a consequence he drew from the principles of the Platonic philosophy, which supposes a pre-existence of souls: accordingly he believed that the soul of Jesus Christ had been united to the Divinity before the incarnation; but then he allowed no distinction of natures in Jesus Christ since his incarnation. This heresy was first condemned in a synod held at Constantinople, by Flavian, in 448; approved by the council of Ephesus, called convenitus latronum, in 449; and re-examined and fulminated in the general council of Chalcedon, in 451. The Eutychians were divided into several branches, as the Agnoetae, Theodosians, Severians, &c. &c. &C. Eutychians was also the name of a sect, half Arian and half Eunomian, which arose at Constantinople in the fourth century.