as a moral matter按道理;原則上
He drinks a cup of hot milk every night on principle. 他每晚照例喝一杯熱牛奶。
I dislike going out for meals in restaurants on principle; why should you pay so much money for food that you could prepare yourself?我就是不喜歡去外面餐館吃飯,幹嗎要花那麼多錢去買那些自己能做的食物呢?