Known primarily through the heresiological writings, Hermogenes goes down in history as a dualist, almost a ditheist, who claimed the doctrine of two coexisting and ingenerated principles : God and the matter. Cleared up the commonplaces and the heresiological strategies of our sources, the analysis of the fragments and of the testimonies about Hermogenes shows that his doctrine was the expression of a specific ontological dualism : far from being an innovative thinker, Hermogenes refused the emerging doctrine of the “creatio ex nihilo” and affirmed the traditional view of the creation as the result of the demiurgic act of God who fashioned and ordered the preexistent matter. According Hermogenes, this dualism did not undermine monotheism, because God and the matter are unequal regarding their essence. It was on the basis of this axiom that he elaborated a theological system characterized by a sophisticate interlacement of anthropological, Christological and soteriological implications.

The term ‘Manichaean’ has come to be regarded as synonymous with a radical dualistic perspective, and is now utilised in all sorts of contexts such as literature and politics. Gardner examines what can be known of the actual teachings of the third‑century sage and self‑declared ‘Apostle of Jesus Christ’ known as Mani or Manichaios. His extant writings are surveyed in order to determine what he says about the nature of God and the origin of matter and evil. Particular attention is given to the terminology and symbolism applied to the idea of two eternal and opposite principles, the kingdoms of light and darkness. Gardner considers possible origins for Mani’s teachings in the Judaeo‑Christian, Gnostic and Iranian traditions ; together with the question of further developments within the community after its founder’s death.

As the most rigorous upholder of monotheism, the pseudo‑Clementine homilist is at strife with the Marcionite dualism. More precisely, he comes up against the Apelles’ doctrine, which is all the more dangerous as it establishes the unicity of God and reduces the demiurge of the world and author of the Law to a created power. The theory of the «false pericopes» of the Scriptures is specially directed against Apelles, in order to protect the identity between the supreme God and the Creator of the world. It seems that the conjectures about the origin of the Evil One, which attempt to avoid a new form of dualism, are also directed towards the refutation of Apelles : to the obedient demiurgical angel is opposed the providential function of the Evil One, who has to put the human beings’ piety to trial ; and against Apelles who maintains the severance between corporeal reality and God’ being, the homilist makes use of the audacious theory of the mixing of the elements to settle both the connaturality of the Evil One and of the body of God and the blamelessness of God with reference to the will of the Tempter, which is contingent.

Of all the approaches to the concept of dualism in Origen’s thought, this article concerns the issue which does not seem very obvious : his understanding of the expression heteros theos. Is it possible to call Jesus “the other God”, existing aside from the only God ? Thanks to the Dialogue with Heraclides, we can judge the profundity of the issue. According to the Dialogue, heteros theos resembles the language used by Marcion, in which “the other God” means the Demiurge, an antagonist of the merciful God. But the expression also invokes the Judeo‑Christian inspired Christology, in which “the other God” signifies a manifestation of the God Jehovah, or a secondary deity, subordinate to Jehovah. In his other writings, Origen usually avoids calling Christ heteros theos, precisely because of the similarity to marcionism and monarchianism. However, forced to resolve the theological problem presented in the Dialogue, Origen decides to explain the meaning of the term “heteros”. His explanations are inspired by Aristotle’s categories, much simplified and illustrated by examples from the Bible. Origen shows that “difference” can be understood as opposition, but there are other possible interpretations of the term. More than anything, it is relative towards a particular characteristic. Origen’s argumentation, in comparison with other discussions concerning the term (Justin Martyr and Tryphon, Peter and Simon the Magician), illustrates that the understanding of God as “different” may lead to the emergence of dualistic concepts, which are often very radical.

Augustine is a particularly interesting author for anyone who wishes to question the topic of dualism, because of the diverse and complex way this topic is adressed in his writings. After having been listening to the Manichean as an “auditor” for almost ten years, he raised many critics against the manichean thesis ; but in spite of this critical position, several of his later opponents, from the Donatist and mostly from the Pelagian heresy, often reproached him to have remained a crypto‑Manichean. This paper focuses on working out the original image Augustine had about the manicheism, as providing a coherent answer to some ethical and metaphysical problems, then as being nothing more than a false response he had to break with. This task will then lead us to question his potential residual manicheism, considering his controversy with Julian of Eclanum, in order to identify the arguments by which Julian supports the accusation of augustinian Manicheism, and to assess the extent to which this accusation is or is not admissible.

The Augustinian definition of the concept of natura rules out any form of dualism : all nature depends on God, it is what God wanted ; but, in the case of man, nature changes according to the actual relation to God, just as the image of God in the soul can be distorted by sin or reshaped by grace. This historical conception of nature sets Augustine against the Manichaean and Pelagian conception of nature as a static datum.

This paper summarises the issues of dualism in the philosophy of Hans Jonas. Dualism was a central topic for him to understand gnosticism in late antiquity, and it became also a key concept to understand moral nihilism of the XXth century. Jonas demonstrates that Heidegger’s thought in Sein und Zeit ‑ which enables him to elaborate the heuristic method to shed light on gnostic dualism ‑ was in fact itself based on a dualistic anthropology. On the one hand, Jonas attempted to reply to it with a philosophical biology ; on the other hand, his reply to the cosmological dualism thanks to his speculative and mythical concept of the weak God.