Overpopulation

<p><em>Scientific Outlook</em> (1931) by Bertrand Russell, page 228:</p>

<p style="padding-left: 30px;">It has hitherto been considered that any man and woman not within the prohibited degrees have a right to marry, and having married have a right, if not a duty, to have as many children as nature may decree. This is a right which the scientific society of the future is not likely to tolerate. In any given state of industrial and agricultural technique there is an optimum density of population which ensures a greater degree of material well-being than would result from either an increase or a diminution of numbers.</p>