Chesterton was a noted opponent of eugenics which was the doctrine to go to in the late 19th century, and reached its gory depths with Nazi race theory and the Holocaust.
Eugenics was the controlled breeding of humans. Positive eugenics advocated interbreeding of the “fittest” (usually white, well educated, members of the Establishment), while negative eugenics discouraged the breeding of the “unfit” (usually the poor, the “feebleminded”, habitual criminals, those lower down the evolutionary ladder). Measures proposed included sterilisation, segregation, even “elimination”.
Chesterton, a devout Catholic, attacked the eugenists for having contempt for the masses of humanity. God’s love was directed towards the poor and afflicted (“blessed are the poor”). He asked for more Christian charity and reminded people that the Bible was harsher towards the rich and powerful.
He denounced the “pseudo-science” behind categories such as “imbeciles” or “morons” , such as used in the flawed IQ tests of the day or in treatment of the mentally ill.
As GK said, we no longer burnt witches, but were increasingly punitive towards the poor, attacking the right to strike, or people’s pleasures such as drinking beer ( a favourite activity of his) or smoking. He saw capitalism as in league with eugenics, aiming to produce a plentiful supply of docile workers, getting rid of “wastage” in the system.
Eugenics also used what Orwell later called Newspeak. For example eugenists did not speak of it being necessary to kill off the old, but spoke of “euthanasia” or remedying “the burden of longevity”. They wanted to eliminate the disabled, even when they were highly intelligent (Stephen Hawkins in our day, consumptive Keats and many other geniuses).
Ever the optimist, GK hoped that humans would embrace ideals of caritas, democracy and Christianity, ideals that had not really been tried. Christianity, for example, “has not been tried and found wanting. It has been found difficult and left untried”.