… is from page 345 of the 1992 collection of some of William Graham Sumner’s best essays, On Liberty, Society, and Politics (Roger C. Bannister, ed.); specifically, this quotation is from an unfinished manuscript, circa 1900-1906:
We must also notice that men have always practiced artificial delusion on each other, both innocently and intentionally. Enthusiasts, dreamers, crafty men, politicians, and demagogs have ruled the masses by suggesting to them utopias and other dreams of bliss, or by exciting their fears of unknown ills. They have always played upon the imaginative element. They can affect the masses far more than the master of science with his demonstrations. Defence against fraud requires the same arms and armor as defence against delusion.
DBx: It cannot be said too often that nearly everything that is possible will never occur. Yet because the range of the possible is indescribably larger than is the range of the plausible (which itself is much larger than is the range of the probable) – and because we humans have both vivid imaginations and strong biases – it’s very easy to incite people to act on irrational hopes and on irrational fears.
Seeing the glass 90 percent full, most people can imagine that glass to be 99 percent full. Many will heedlessly risk draining the glass in pursuit of the possible but extraordinarily implausible prospect of achieving near-perfection. Others, seeing the same 90-percent-filled glass, have their imaginations stirred by those who insist that the glass will be drained by some calamity – a calamity that is possible but highly implausible. Nevertheless, to prevent the highly implausible calamity, many people whose fears are aroused will recklessly endorse measures that with a not-insignificant probability will bring about a calamity very much like the one that the measures are meant to prevent.