Professor Peter Singer talar ibland om ”expanding circles of compassion”: att de som omfattas av vår omsorg blir fler och fler över tid. Charles Darwin gav uttryck för en liknande, naturalistisk förståelse, och precis som Singer menade han att människor kommer att bry sig om och i sin moralsyn inkludera andra djur än sig själva:
[T]he social instincts which no doubt were acquired by man, as by the lower animals, for the good of the community, will from the first have given to him some wish to aid his fellows, and some feeling of sympathy. Such impulses will have served him at a very early period as a rude rule of right and wrong. But as man gradually advanced in intellectual power and was enabled to trace the more remote consequences of his actions; as he acquired sufficient knowledge to reject baneful customs and superstitions; as he regarded more and more not only the welfare but the happiness of his fellow-men; as from habit, following on beneficial experience, instruction, and example, his sympathies became more tender and widely diffused, so as to extend to the men of all races, to the imbecile, the maimed, and other useless members of society, and finally to the lower animals, – so would the standard of his morality rise higher and higher.*
*Darwin, Charles, (1871). The Descent of Man, and Selection in Relation to Sex. London: John Murray: 103.
Se även de tidigare inläggen ”Gränsen för omtanke”, ”Varifrån kommer moral?” och ”Djurens lycka”.