3.  This term also corrects the error of Sabellius, for it removes the idea of the identity of the hypostases, and introduces in perfection the idea of the Persons.  For nothing can be of one substance with itself, but one thing is of one substance with another.  The word has therefore an excellent and orthodox use, defining as it does both the proper character of the hypostases, and setting forth the invariability of the nature.  And when we are taught that the Son is of the substance of the Father, begotten and not made, let us not fall into the material sense of the relations.  For the substance was not separated from the Father and bestowed on the Son; neither did the substance engender by fluxion, nor yet by shooting forth cf. Luke xxi. 30. as plants their fruits.  The mode of the divine begetting is ineffable and inconceivable by human thought.  It is indeed characteristic of poor and carnal intelligence to compare the things that are eternal with the perishing things of time, and to imagine, that as corporeal things beget, so does God in like manner; it is rather our duty to rise to the truth by arguments of the contrary, and to say, that since thus is the mortal, not thus is He who is immortal.  We must neither then deny the divine generation, nor contaminate our intelligence with corporeal senses.