India, Aug. 8 -- The human being did not evolve to stay fixed to one patch of soil. Movement is prakriti; it is natural, older than any border ever drawn on a map. You will watch a migratory bird cross a continent and feel something lift in you, but let the same instinct arrive on two legs, with a bag over its shoulder, and the feeling curdles into suspicion, even derision. Why the difference? Why not ban the birds too, and scold them for arriving uninvited at this lake or that field? They come because that is how prakriti moves, and you are not meant to remain confined to the village you were born in.

Late in July, some sixty thousand people threw themselves at the fence between Morocco and the small Spanish enclave of Ceuta, and more t...