The truth for which they contended, which was enshrined in their sacred writings, was that 'the Father is God, the Son is God, and the Holy Ghost is God. And yet they are not three Gods, but one God.' But the Fathers do not treat this doctrine merely as a revealed mystery, still less as something which complicates the simple teaching of Monotheism, but as the condition of rationally holding the Unity of God. 'The Unity which derives the Trinity out of its own self,' says Tertullian, 'so far from being destroyed, is actually supported by it[111].' 'We cannot otherwise think of One God,' says Hippolytus, 'but by truly believing in Father, and Son, and Holy Ghost[112].' 'The supreme and only God,' says Lactantius, 'cannot be worshipped except through the Son. He who thinks that he worships the Father only, in that he does not worship the Son also, does not worship the Father[113]. 'Without the Son the Father is not,' says Clement of Alexandria, 'for in that He is a Father He is the Father of the Son, and the Son is the true teacher about the Father[114].' So Origen argues,--If God had ever existed alone in simple unity and solitary grandeur, apart from some object upon which from all eternity to pour forth His love, He could not have been always God. His love, His Fatherhood, His very omnipotence would have been added in time, and there would then have been a time when He was imperfect. 'The Fatherhood of God must be coeval with His omnipotence; for it is through the Son that the Father is Almighty[115].' This was the line of argument afterwards developed by S. Athanasius when he contended against the Arians that the Son was the reality or truth[116] of the Father, without whom the Father could not exist; and by S. Augustine, when he argues that love implies one who loves and one who is loved, and love to bind them together[117]. Even one so unphilosophically minded as Irenaeus[118], cannot but see in the Christian doctrine of the relation of the Father and the Son, the solution of the difficulty about the infinity of God: 'Immensus Pater in Filio mensuratus; mensura Patris Filius.' While philosophy with increasing hopelessness was asking, How can we have a real unity which shall be not a barren and dead unity, but shall include differences? Christianity, with its doctrine of God, was arguing that that which was an unsolved contradiction for non-Christian thought, was a necessary corollary of the Christian Faith[119].