His chief treatise is entitled "Difficulties and Solutions of First Principles" (). It examines the nature and attributes of God and the human soul. This examination is, in two respects, in striking contrast to that of certain other Neoplatonist writers. It is conspicuously free from Oriental mysticism, and it contains no polemic against Christianity, to the doctrines of which, in fact, there is no allusion. Hence the charge of impiety which Photius brings against him. In this treatise Damascius inquires into the first principle of all things, which he finds to be an unfathomable and unspeakable divine depth, being all in one, but undivided. His main result is that God is infinite, and as such, incomprehensible; that his attributes of goodness, knowledge and power are credited to him only by inference from their effects; that this inference is logically valid and sufficient for human thought. He insists throughout on the unity and the indivisibility of God. This work is, moreover, of great importance for the history of philosophy, because of the great number of accounts which it contains concerning former philosophers.