2.  Because even at that time there were men who asserted the Son to have been brought into being out of the non-existent, the term homoousion was adopted, to extirpate this impiety.  For the conjunction of the Son with the Father is without time and without interval.  The preceding words shew this to have been the intended meaning.  For after saying that the Son was light of light, and begotten of the substance of the Father, but was not made, they went on to add the homoousion, thereby showing that whatever proportion of light any one would attribute in the case of the Father will obtain also in that of the Son.  For very light in relation to very light, according to the actual sense of light, will have no variation.  Since then the Father is light without beginning, and the Son begotten light, but each of Them light and light; they rightly said “of one substance,” in order to set forth the equal dignity of the nature.  Things, that have a relation of brotherhood, are not, as some persons have supposed, of one substance; but when both the cause and that which derives its natural existence from the cause are of the same nature, then they are called “of one substance.”