在基督教里，認為耶穌的本性仍和神性在一起而非人性，即使他已經在人間實現了人的生死禍福。一性論學說宣稱，在耶穌基督人的裡面只有里一個神性而非兩個，即神性和人性，正如451年卡爾西頓宗教會議上所宣稱的一樣。
一性論派,英譯原文,
一性論派
在4、5和6世紀裡基督人性的學說的發展裡面，一些有分歧的傳統逐漸出現。卡爾西頓會議通過了這樣一個法令，即“基督已經確認兩由性，沒有被混合、改變或者是分離。”這個陳述在一定程度上是與諾斯替說學相對的——基督身上的兩性仍然是分離的，並且它們是發揮作用的兩個人——一定程度上反對理論上的修道士優提克斯單純的位置，在448年優提克斯因為教授下列理論而遭到譴責，即在道成肉身之後，基督只有一性，並且肉身的基督的人性和其他人所構成的物質不同。政治和教會的對抗和理論一樣在卡爾西頓驅逐並開除Dioscorus的決定中起到了重要的作用。支持Dioscyus並堅持他的教導與亞歷山大里亞的聖·西里爾的正統學說是一致的教派被貼上了一性論派的標籤。
這個標籤也同形形色色的理論家和群體相聯繫，雖然他們中有些被稱為一性論者，如著名的安條克的塞維魯，就拒絕自身就自相矛盾的卡爾西頓用語。大部分的現代學者同意塞維魯同Dioscrus一樣，可能反對在他們對在基督那裡上帝和人的團體的親密關係多於在任何基督人性和人類是同質的拒絕中被界定為正統的理論。
在近代，通常被界定為一性論派的這些教會（亞美尼亞使徒派，埃及正統基督派，衣索比亞正統派，敘利亞正統派）作為在耶穌基督人的學說上的本質的正統，基本已經被羅馬天主教、東正教和新教國家所接受。
英譯原文
in Christianity, one who believed that Jesus Christ's nature remains altogether divine and not human even though he has taken on an earthly and human body with its cycle of birth, life, and death. Monophysite doctrine thus asserted that in the Person of Jesus Christ there was only one (divine) nature rather than two natures, divine and human, as asserted at the Council of Chalcedon in 451. In the development of the doctrine of the Person of Christ during the 4th, 5th, and 6th centuries, several divergent traditions had arisen. Chalcedon adopted a decree declaring that Christ was to be “acknowledged in two natures, without being mixed, transmuted, divided, or separated.” This formulation was directed in part against the Nestorian doctrine—that the two natures in Christ had remained separate and that they were in effect two Persons—and in part against the theologically unsophisticated position of the monk Eutyches, who had been condemned in 448 for teaching that, after the Incarnation, Christ had only one nature and that, therefore, the humanity of the incarnate Christ was not of the same substance as that of other men. Political and ecclesiastical rivalries as well as theology played a role in the decision of Chalcedon to depose and excommunicate the patriarch of Alexandria, Dioscorus (d. 454). The church that supported Dioscorus and insisted that his teaching was consistent with the orthodox doctrine of St. Cyril of Alexandria was labeled monophysite.
The label also was attached to various theologians and groups, although some who were called monophyste, notably Severus of Antioch (d. 538), repudiated the terminology of Chalcedon as self-contradictory. Most modern scholars agree that Severus as well as Dioscorus probably diverged from what was defined as orthodoxy more in their emphasis upon the intimacy of the union between God and man in Christ than in any denial that the humanity of Christ and that of mankind are consubstantial.
In modern times, those churches usually classified as monophysite (the Armenian Apostolic, Coptic Orthodox, Ethiopian Orthodox, and Syrian Orthodox) are generally accepted by Roman Catholic, Eastern Orthodox, and Protestant Christendom as essentially orthodox in their doctrine of the Person of Jesus Christ.
