It was not, in fact, till a rather later stage in the growth of science, either in the old world, or in our own, that anyone troubled himself about the existence of such unity at all. That men of alien blood should behave in alien and incomprehensible ways seemed to the Greek and to the navigators of the Renaissance equally natural. And Herodotus and Bodin, to name only pioneers and masters, are agreed as to the cause. Variety in Man's behaviour is no impish trick of original sin: it is the response of his single reason to variety in Nature. Only when experience added intimacy with alien individuals to observations of their habits of life, did a common humanity in their behaviour begin to be so frequent and obvious as to cause surprise. Acquiescence in the discovery is implicit in Thucydides and Hobbes, and confessed in Aristotle and Locke. Had Europe broken into the Great East in Locke's day, as the Greeks broke into Persia in Aristotle's, we might have had completer analogy between the ethnology of Montesquieu and that of Eratosthenes than we can actually trace. The defect in the writer of the _Lettres Persanes_ is in his knowledge of Persia, not of Paris and London: Eratosthenes, as we remember, was born in Cyrene and worked in Alexandria. MAN IN CONFLICT WITH NATURE IN THE NORTH-WEST QUADRANT OF THE OLD WORLD We come now, from this rather general survey of human faculty, to the more pertinent question, what sort of unity do we find in human achievement within that region, or rather within those regions, of the Old World where the stream-heads of our modern culture seem to take their rise? The qualification which has slipped from my pen is half the answer already, for we are to deal not with one homogeneous region but with a cluster of regions in all climates from Arctic tundra to Sahara and the Nile, and in all altitudes from alpine to maritime. Unity of prehistoric culture, in such conditions, can at best be but a question of degree. Modern ethnology, emancipated from a belief in an immediate consanguinity of mankind, by the spread of less infantile views about Noah's Ark, goes on to question the sufficiency of language as a bond of union, and forthwith stumbles over the Tower of Babel.