There are those who would regard all national barriers and organization as somewhat of an obstruction, who would prefer a simple internationalism to the world as we know it, with its pent-up passions and attachments, its constant liability to explosion, its slow progress by tortuous channels towards the larger view and the surer hold. Many reformers, from Plato downwards, have taken up a similar attitude in regard to the smaller institution, the family, which is often found to be an obstruction in the way of short cuts to social utopias at home. Kant's ideal of a cosmopolitan constitution as the goal of all human effort rather leans to this side of the balance. But a due balance must be kept and the full value both of family and nation maintained against theories or tendencies which would roll us all out into cosmopolitan items. A glance at other elements which go to make up the unity of European society will tend to correct the perspective. The unity of the Roman Empire was mainly political and military. It lasted for between four and five hundred years. The unity which supervened in the Catholic Church was religious and moral and endured for a thousand. Less binding on one side, it was more searching and pervasive on others, and though now broken, it still remains in full force over many millions of minds, while the Roman political and legal structure has to be sought for in formal institutions which have absorbed its spirit and transformed its letter. But beyond the actual fabric of the Church itself we have the multitude of cognate and derivative institutions which have served the cause of unity in the moral and intellectual sphere. We shall speak later of the more perfect and lasting unity of science. The universities in the Middle Ages and the Renascence tended to the same end, using a material in philosophy and theology which was bound to wear out with the spread of knowledge and the flux of time. But in their prime they succeeded in producing a more complete community of scholars than has perhaps been ever witnessed in Europe before or since. Then as always the realm of the genuine love of truth, or even of honest disputation, was independent of differences of race or political boundaries, and the scholar went from Oxford to Paris, or from Rotterdam to Bologna, solely to widen his mind or to sit at the feet of some world-famous teacher. And the wandering scholar was by no means the only social link. Many of the trade-routes surprise us by the length and adventurousness of their course. Amber from the Baltic found its way to the south of Italy and Spain, while small boats from Ireland were brought into the mouths of the Loire and the Garonne when the coasts of the Channel were impassable through barbarians from the North.