I can't speak for anyone else, obviously, but I find I rarely need to stop and asses ethical situations against some system of morality that I may or may not stand by as a matter of principle. I just seem to do it, or not (whatever is warranted), in the same way I blink my eyes or breathe in and out. It couldn't be - <gasp> - instinctive, do you suppose?
At the age of five, Skagra decided emphatically that God did not exist. This revelation tends to make most people in the universe who have it react in one of two ways - with relief or with despair. Only Skagra responded to it by thinking, 'Wait a second. That means there's a situation vacant.'