 The real deviation from Aristotelianism is Epistle 20 On nature. In that it shows how nature as taught by Aristotle was received and theorized by the authors, this treatise could serve as the perfect introduction to the section on natural sciences. However, its main part regards angelology. It also introduces a Neoplatonically inspired conception of Nature, suggestive of Ismâ‘îli philosophical positions, as Abû Ya‘qûb al-Sijistânî's representation of Nature as “agent power” and “principle of movement”.