Nothing shocks our moral feelings so deeply as cruelty does. We can forgive every other crime, but not cruelty. The reason for this is that it is the very opposite of compassion.
Arthur SchopenhauerJust as a stream flows smoothly on as long as it encounters no obstruction, so the nature of man and animal is such that we never really notice or become conscious of what is agreeable to our will; if we are to notice something, our will has to have been thwarted, has to have experienced a shock of some kind.
Arthur Schopenhauer