We cannot reason of these things. But this I know—and this may by all men be known—that no good or lovely thing exists in this world without its correspondent darkness; and that the universe presents itself continually to mankind under the stern aspect of warning, or of choice, the good and the evil set on the right hand and the left.
John Ruskin (Modern Painters, V, 19).
It is one of the arguments in Plato’s Phaedo that the soul must survive, since otherwise terribly wicked and cruel men would escape retribution; annihilation would be a good thing for them.
All creatures and all objects, in degree,
Are friends and patrons of humanity.
There are to whom the garden, grove and field
Perpetual lessons of forbearance yield;
Who would not lightly violate the grace
The lowliest flower possesses in its place,