It is by the One that all beings are being, both those which are primarily being and those which are in any sense said to be amongst beings. For what could anything be if it was not one? For if things are deprived of the One which is predicated of them, they are not those things. (Enn. VI.9[9].1.1-4)1

Plotinus’ programmatic treatise On the Good or the One begins with these words. It summarizes the basis of his “philosophy of the One” (Enn. VI.9[9].3.14), as he essentially characterizes his own thought in the shortest possible way. Let us analyse this claim in more detail.