But the controversies did not so much end with Origen as begin with him. From that time they were mostly internal to Christianity. But their elements were Greek in origin. The conceptions which were introduced into the sphere of Christian thought were the current ones of philosophy. In Christian theology that philosophy has survived. But although it would be beyond our present purpose to describe the Christological controversies which followed the final dominance in the Church of the transcendental idea of God, it is within that purpose to point out the Greek elements, confining ourselves as far as possible to the later Greek uses of the terms. _Ousia_ (οὐσία) is used in at least three distinct senses: the distinction is clearly phrased by Aristotle.[548] (_a_) It is used as a synonym of _hylê_, to designate the material part of a thing. The use is most common among the Stoics. In their monistic conception of the universe, the visible world was regarded as the _ousia_ of God.[549] In the same way Philo speaks of the blood as the material vehicle, τὸ οὐσιῶδες, of the vital force.[550] Hence in both philosophical and Christian cosmologies, _ousia_ was sometimes used as interchangeable with _hylê_, to denote the matter out of which the world was made. (_b_) It is used of matter embodied in a certain form: this has since been distinguished as the _substantia concreta_. In Aristotle, a sensible material thing, a particular man or a particular horse, which in a predication must always be the subject and cannot be a predicate, is an _ousia_ in the strictest sense.[551] (_c_) It is used of the common element in the classes into which sensible material things may be grouped: this has since been distinguished as the _substantia abstracta_: in the language of Aristotle, it was the form (εἶδος), or ideal essence (τὸ τί ἦv εἶναι).[552] This sense branched out into other senses, according as the term was used by a realist or a nominalist: to the former it was the common essence which exists in the individual members of a class (τὸ εἶδος τὸ ἐνόν),[553] and not outside them (since ἀδύνατον χωρὶς εἶναι τὴν οὐσίαν καὶ οὗ ἡ οὐσία);[554] or which exists outside them, and by participation in which they are what they are: this latter is Plato’s conception of εἶδος,[555] and of its equivalent οὐσία. To a nominalist, on the other hand, _ousia_ is only the common name which is predicable in the same sense to a number of individual existences.[556]