As a result of his condemnation, many of his works were not copied during the Middle Ages and were subsequently lost. Of his lost compositions we can gather a partial list from the citations of ancient authors which includes "On Dogmas, On The Death of Young Children, Against the Arians, First Word," and others. One of Didymus's lost works is a commentary on Origen's "First Principles" which, according to Jerome, tried to interpret an orthodox understanding of the Trinity from Origen's theology. In it, he assumed the pre-existence of souls and Apocatastasis. He staunchly defended the doctrine of the Trinity. He argued that Christ's body and soul were human, but that Christ was sinless.