The world is faced at the present day with two antithetical dangers. There is the risk, which has begun to sink into popular consciousness, that the human race may put an end to itself by a too lavish use of H-bombs. There is an opposite risk, not nearly so widely appreciated, that the human population of our planet may increase to the point where only a starved and miserable existence is possible except for a small minority of powerful people. These risks, though diametrically opposed to each other, are nevertheless connected. Nothing is more likely to lead to an H-bomb war than the threat of universal destitution through over-population. It is with the nature of this threat and with the means for averting it that I shall be concerned in what follows.