This Leucius wrote a work, entitled, according to Photius, αἱ τῶν Ἀποστόλων περίοδοι, , now lost, containing the Acts of the Apostles, Peter, John, Andrew, Thomas, and Paul. Photius criticises the style as in many places too familiar, and condemns the sentiments as heretical, self-contradictory, and absurd. The writer distinguished between the God of the Jews (whom he designated as malignant, and whose minister Simon Magus was) and Christ (whom he called " the Good One"). He denied the reality of Christ's human nature, and affirmed that he was not crucified, but that another suffered in his place. He condemned marriage as altogether unlawful. Both Augustin and the author of the book (ll. cc.) cite a passage from this work, which they call and it is evident from what they say that it was much esteemed among the Manichaeans, though rejected by the great body of Christians.

Pope Innocent I., or the writer, whether Innocentius or not, of the ascribes to " one Leucius" some apocryphal writings extant in his time (Innocent died A. D. 417), under the names of Matthew, of James the Less, and of Peter and John: and in the prefatory letters to the apocryphal (Fabric. vol. i. p. 19), which pretend to be addressed to or written by Jerome, by whom the itself (which was ascribed to the evangelist Matthew) was professedly translated from the Hebrew into Latin, it is stated that a work on the same subject, or rather the same work much interpolated, had been published by Seleucus, a Manichaean. We are not aware that the date of these pseudo-Hieronymian letters is known, but they indicate that such a work by Seleucus was then in existence; and this Seleucus is by many critics identified with our Leucius. Huet supposes that the apocryphal writings ascribed to Leucius by pope Innocent included the given by Fabricius (l c. p. 66); but if there be any foundation for this opinion, Leucius must have lived a century before Manes, as indeed Grabe supposes that he did. Fabricius, however, decidedly rejects the opinion of Huet. Grabe ( lib. 1. c.17) cites from a MS. at Oxford, containing a passage which resembles part of the (100.49), but does not exactly agree with it.