Sin? Sin like love was a word hard to define. It came in two bitter but vastly different flavors. The first lay in violating the taboos of your tribe … The other meaning of sin was easier to define because it was not molded by the murky concepts of religion and taboo: Sin is behavior that ignores the welfare of others.

Robert A. Heinlein (1907-1988) American writer

Time Enough For Love (1973)