Abstract: It is evident that both law and morality serve to channel our behavior. Law accomplishes this primarily through the threat of sanctions if we disobey legal rules. Morality too involves incentives: bad acts may result in guilt and disapprobation, and good acts may result in virtuous feelings and praise. These two very different avenues of effect on our actions are examined in this article from an instrumental perspective. The analysis focuses on various social costs associated with law and morality, and on their effectiveness, as determined by the magnitude and likelihood of sanctions and by certain informational factors. After the relative character of law and of morality as means of control of conduct is assessed, consideration is given to their theoretically optimal domains - to where morality alone would appear to be best to control behavior, to where morality and the law would likely be advantageous to employ jointly, and to where solely the law would seem desirable to utilize. The observed pattern of use of morality and of law is discussed, and it is tentatively suggested that the observed and the optimal patterns are in rough alignment with one another.