 William of Auvergne (d. 1249) is much attracted by Arabic metaphysical and pyschological theories (which he often indiscriminately attributes to “Aristotle and his followers”) and discusses them at length, but often rejects them in the end as conflicting with Christian faith. In On the Universe (De universo II.1), William discusses and rejects the Avicennian emanation system: the necessity of causation through the first cause; the emanation of the intelligences from the first intelligence down to the active intellect; the active intellect as the efficient cause of human souls. He nevertheless tacitly adopts the metaphysical principle “From one arises only one” (de uno non nisi unum) from Avicenna (Teske 1993), in particular within the context of Trinitarian theology (Fischer 2015), and describes the first cause as the “being necessary through itself” (Teske 2002, Fischer 2018).