 Hence, through the concept of emanation, Avicenna explains the God-world relationship and, more generally, efficient causality. The causality of motion (taḥrīk) and of influence (taʾaṯṯur) are both added to and subsumed under the causality of emanation, which is sustained by the ideas of both donation and reception. With his metaphysics Avicenna provides a foundation for every level of his theory: physics and then psychology, gnoseology or epistemology, prophecy (Ilāhiyyāt, X, 2–3) and even eschatology (Ilāhiyyāt, IX, 7; Michot 1986) find their ultimate explanation in the metaphysical concept of the flow of forms. Consequently, if the Ilāhiyyāt of the Kitāb al-Šifāʾ and the metaphysical parts of the other summae (Salvation, Remarks, Science, Guidance) together with the Kitāb al-Taʿlīqāt (The Book of Notes) and other writings like the Kitāb al-Mabdaʾ wa-l-maʿād (The Book of Provenance and Destination), are essential to the study of metaphysics, it is no exaggeration to state that every work Avicenna devoted to philosophy can be relevant to the understanding of his metaphysical ideas and that metaphysical works clarify the other parts of Avicenna’s system: metaphysics is omni-comprehensive.