The neo-Platonic school was founded by Ammonius Saccas, but really takes its definite form under _Plotinus_ (d. 269 A.D.). In sketching in brief outline the leading principles of this system we shall confine ourselves to the last three books of the _Enneads_ (iv-vi) as these, in the abridged form known as the “Theology of Aristotle” formed the main statement of neo-Platonic doctrine known to the Muslim world. In the teaching of Plotinus God is the Absolute, the First Potency (_Enn._ 5. 4. 1.), beyond the sphere of existence (id. 5. 4. 2.), and beyond reality, that is to say, all that we know as existence and being is inapplicable to him, and he is therefore unknowable, because on a plane which is altogether beyond our thought. He is unlimited and infinite (id. 6. 5. 9.) and consequently One, as infinity excludes the possibility of any other than himself on the same plane of being. Yet Plotinus does not allow the numeral “one” to be applied to God as numerals are understandable and refer to the plane of existence in which we have our being, so that “one” as a mere number is not attributed to God, but rather singularity in the sense of an exclusion of all comparison or of any other than himself. As Absolute God implies a compelling necessity so that all which proceeds from him is not enforced but is necessarily so in the sense that nothing else is possible; thus, for example, it results from him that two sides of a triangle are greater than the third side, they are not forced into greater length, but in the nature of things must be so, and this necessary nature has its compelling source in the First Cause. Yet Plotinus will not allow us to say that God “wills” anything, for will implies a desire for what is not possessed or is not yet present (id. 5. 3. 12); will operates in time and space, but necessity has for ever proceeded from the Eternal One who does not act in time. Nor can we conceive God as knowing, conscious, or thinking, all terms which describe our mental activities in the world of variable phenomena; he is all-knowing by immediate apprehension ([Greek: athroa epibolê] ἀθρόα ἐπιβολή) which in no way resembles the operation of thought but is superconscious, a condition which Plotinus describes as “wakefulness” ([Greek: egrêgorsis] ἐγρήγορσις), a perpetual being aware without the need of obtaining information.