The right to have children should be a marketable commodity, bought and traded by individuals but absolutely limited by the state. - Kenneth E. Boulding

Another indication of the magnitude of the present transition is the fact that, as far as many statistical series related to activities of mankind are concerned, the date that divides human history into two equal parts is well within living memory.

...the perception of potential threats to survival may be much more important in determining behavior than the perceptions of potential profits, so that profit maximization is not really the driving force. It is fear of loss rather than hope of gain that limits our behavior

Mathematicians themselves set up standards of generality and elegance in their exposition which are a bar to understand.