Proposition 10 of the Liber de causis proposes that “all intelligence is full of forms”. The causally higher intellects contain more universal forms, from these derive those intelligences which contain less universal forms. Explaining it, Aquinas first notes his agreement with Proclus that the “superiores habent formas magis universales, inferiores vero minus universales” and then tells us that Denys says the same in the Celestial Hierarchy: ubi dicit quod cherubim ordo participat sapientia et cognitione altiori, sed inferiores substantiae participant sapientia et scientia particulariori. Aquinas proceeds to set out his general doctrine on the role of the angelic illuminations in bringing the divine knowledge and purposes to us.
By the point at which he is explaining proposition 19, Thomas can draw together what we have found in propositions 5 and 10 and bring before us a corollary of the lex divinitatis. Proposition 19 distinguishes between, and connects in a descending causal chain, “intelligentia divina”, receiving the first good gifts from the first cause, “intelligentia tantum”, which has between it and the first cause a mediating intelligence, “anima intelligibilis”, and “anima tantum”, from which we arrive at “corpora naturalia tantum”. Thomas’ explanation refers us to proposition 106 of the Elements (on intermediates between what is wholly eternal and what is in time) and then to the De Divinis Nominibus of Denys. There he finds the law that “fines primorum coniunguntur principiis secundorum”. He compares the “divinae intelligentiae” of the Liber de causis to the Dionysian “supremi angeli sunt quasi in vestibulis deitatis collocati”. The seraphim are the very highest of these. In making the categories of Proclus, of the Liber de causis, and of Denys cohere, he shrewdly places in the rank of mere intellects those angels who intermediate between the highest and ensouled humans: Inferiores vero intellectus qui non pertingunt ad tam excellentem participationem divinae similitudinis sunt intellectus tantum, non habentes illam divinam dignitatem.