The real trouble is that “kindness” is a quality fatally easy to attribute to ourselves on quite inadequate grounds. Everyone feels benevolent if nothing happens to be annoying him at the moment. Thus a man easily comes to console himself for all his other vices by a conviction that “his heart’s in the right place” and “he wouldn’t hurt a fly,” though in fact he has never made the slightest sacrifice for a fellow creature. We think we are kind when we are only happy: it is not so easy, on the same grounds, to imagine oneself temperate, chaste, or humble. You cannot be kind unless you have all the other virtues. If, being cowardly, conceited and slothful, you have never yet done a fellow creature great mischief, that is only because your neighbour’s welfare has not yet happened to conflict with your safety, self-approval, or ease. Every vice leads to cruelty.

C.S. Lewis (1898-1963) English writer and scholar [Clive Staples Lewis]
The Problem of Pain (1940)