Throughout history and in virtually every part of the earth men have lived and multiplied, and have created some form of culture. Always and everywhere they have found their means of subsistence and something to spare. Civilisations have been built up, have flourished, and, in most cases, have declined and perished. This is not the place to discuss why they have perished; but we can say: there must have been some failure of resources. In most instances new civilisations have arisen, on the same ground, which would be quite incomprehensible if a had been simply the material resources that had given out before. How could such resources have reconstituted themselves?