“With a higher moral nature will come a restriction on the multiplication of the inferior.”

"Passages from the life of a philosopher", Appendix, p. 490
Passages from the Life of a Philosopher (1864)

Women (1978)

The Nightmares of a Journalist (1991)

XI, 10
Meditations (c. 121–180 AD), Book XI

Interview in the documentary-film What the Health by Kip Andersen (2017).

Meditations. xi. 10.
Bartlett's Familiar Quotations, 10th ed. (1919)

If any creature, by its very nature, causes terrible suffering, albeit unwittingly, is it morally wrong to change that nature? If a civilised human were to come to believe s/he had been committing acts that caused grievous pain for no good reason, then s/he would stop - and want other moral agents to prevent the recurrence of such behaviour. May we assume that the same would be true of a lion, if the lion were morally and cognitively "uplifted" so as to understand the ramifications of what (s)he was doing? Or a house cat tormenting a mouse? Or indeed a human sociopath?

" Reprogramming Predators https://www.hedweb.com/abolitionist-project/reprogramming-predators.html", BLTC Research, 2009

To W. Lutoslawski (6 May 1906)
1920s, The Letters of William James (1920)
Context: Most people live, whether physically, intellectually or morally, in a very restricted circle of their potential being. They make use of a very small portion of their possible consciousness, and of their soul's resources in general, much like a man who, out of his whole bodily organism, should get into a habit of using and moving only his little finger. Great emergencies and crises show us how much greater our vital resources are than we had supposed.

Source: Words of a Sage : Selected thoughts of African Spir (1937), p. 60 - Hélène's Claparède-Spir underlined.