I think we must accept this view of the importance of the direct action of physical environment on the minds of individuals. To deny, as Hegel did, the important influence of physical environment upon the development of Greek culture, because the Turks have enjoyed a similar climate without producing a similar culture, is unreasonable. The progress of civilisation has always been the result of a multiplicity of causes and conditions; and we cannot deny all importance to any one, whether race or climate or social organisation or religion or any other, because in some particular instance it has failed to produce the progress of which in other instances it has been one of a number of co-operating causes. The diversity and small scale of the physical features of South and Western Europe has favoured the progress of the intellectual tradition in another important way. The land is divided by natural barriers into a number of natural territories, the population of each of which has naturally tended to become one nation and to develop a national culture. In this way there arose a number of nations and States in close proximity with one another, yet each developing along its own lines. When the development of wealth and commerce brought these diversified cultures into friendly intercourse with one another, the exchange of ideas and the general imitation of the useful arts of one people by its neighbours must have made very strongly for progress; the culture of each of a group of neighbouring peoples no longer progressed only by the addition of the ideas and inventions of its own exceptional intellects, but each group had the opportunity of selecting and imitatively adopting whatever seemed to them best among the ideas, the arts and inventions of the neighbouring peoples. It is generally admitted that this was one of the main conditions of the rapid development of the culture of the ancient Greeks, situated as they were within easy reach of several of the oldest civilisations, those of Egypt and of South-Eastern Asia; they were also within reach of a number of less civilised peoples, and therefore enjoyed opportunities for trade of a kind which, being peculiarly lucrative, has in all ages hastened the acquisition of wealth and capital and stimulated the development of commerce. All the most progressive European peoples have enjoyed similar advantages; and it has been maintained with some plausibility that the principal cause of the shifting of the centre of progressive civilisation from the Eastern Mediterranean to the west of Europe has been the improvement of the art of navigation and the discovery of the New World and of the sea route to Asia and the East Indies; for these gave the western countries the most advantageous positions for the conduct of a world wide commerce. No doubt the factor mentioned has been important in producing this change.