results follow, which have their importance.  In the first place, we can hardly say that the Middle Ages have any conception of the State.  The notion of the State involves plurality; but plurality is ex hypothesi not to be found.  The notion of the State further involves sovereignty, in the sense of final and complete control of its members by each of a number of societies.  But this, again, is ex hypothesi not to be found.  There is one final control, and one only, in the mediaeval system—­the control of Christian principle, exerted in the last resort, and exerted everywhere, without respect of persons, by the ruling vicar of Christ.  But if plurality and sovereignty thus disappear from our political philosophy, we need a new orientation of all our theory.  We must forget to speak of nations.  We must forget, as probably many of us would be very glad to forget, the claims of national cultures, each pretending to be a complete satisfaction and fulfilment of the national mind; and we must remember, with Dante, that culture (which he called ‘civility’) is the common possession of Christian humanity.  We must even forget, to some extent, the existence of different national laws.  It is true that mediaeval theory admitted the fact of customary law, which varied from place to place.  But this customary law was hardly national:  it varied not only from country to country, but also from fief to fief, and even from manor to manor.  It was too multiform to be national, and too infinitely various to square with political boundaries.  Nor was customary law, in mediaeval theory, anything of the nature of an ultimate command.  Transcending all customs, and supreme over all enactments, rose the sovereign majesty of natural law, which is one and indivisible, and runs through all creation.  ’All custom,’ writes Gratian, the great canonist, ’and all written law, that are adverse to natural law, are to be counted null and void.’  Here, in this conception of a natural law upholding all creation, we may find once more a Stoic legacy to the Christian Church.  ’Men ought not to live in separate cities, distinguished one from another by different systems of justice’—­so Zeno the Stoic had taught—­’but there should be one way and order of life, like that of a single flock feeding on a common pasture.’  Zeno, like St. Paul, came from Cilicia.[20] Like St. Paul, he taught the doctrine of the one society, in which there was neither Jew nor Gentile, neither Greek nor barbarian.  We shall not do wrong to recognize in his teaching, and in that of his school, one of the greatest influences, outside the supreme and controlling influence of the Christian principle itself, which made for the dominance of the idea of unity in mediaeval thought.