Iamblichus’s account of theurgy is repeated in more condensed form by Proclus (412-485) in a brief treatise or fragment which is extant only in its Latin translation by the Florentine humanist Ficinus, entitled _De sacrificio et magia_.[1435] Neither magic nor theurgy, however, is mentioned by name in the Latin text. Proclus states that the priests of old built up their sacred science by observing the sympathy existing between natural objects and by arguing from manifest to occult powers. They saw how things on earth were associated with things in the heavens and further discovered how to bring down divine virtue to this lower world by the force of likeness which binds things together. Proclus gives several examples of plants, stones, and animals which evidence such association. The cock, for instance, is reverenced by the lion because both are under the same planet, the sun, but the cock even more so than the lion. Therefore demons who appear with the heads of lions (_leonina fronte_) vanish suddenly at the sight of a cock unless they chance to be demons of the solar order. After thus indicating the importance of astrology as well as occult virtue in theurgy or magic, Proclus tells how demons are invoked. Sometimes a single herb or stone “suffices for the divine work”; sometimes several substances and rites must be combined “to summon that divinity.” When they had secured the presence of the demons, the priests proceeded, partly under the instruction of the demons and partly by their own industrious interpretation of symbols, to a study of the gods. “Finally, leaving behind natural objects and forces and even to a great extent the demons, they won communion with the gods.” [Sidenote: Neo-Platonic account of magic borrowed by Christians.] Despite the writings of Porphyry and other Neo-Platonists against Christianity, much use was made by Christian theologians of the fourth and fifth centuries of the Neo-Platonic accounts of magic, astrology, and divination, especially of Porphyry’s _Letter to Anebo_. Eusebius in his _Praeparatio Evangelica_[1436] made large extracts from it on these themes and also from Porphyry’s work on the Chaldean oracles. Augustine in _The City of God_[1437] accepted Porphyry as an authority on the subjects of theurgy and magic. On the other hand, we do not find the Christian writers repeating the attitude of Plotinus that the life of reason is alone free from magic, except as they substitute the word “Christianity” for “the life of reason.” [Sidenote: Neo-Platonists and alchemy.]