If this were strictly interpreted according to its form, it would mean that three things go to constitute virtue, any one of which being absent, we should not have virtue. Doing good to mankind alone is not virtue, unless coupled with a divine requirement; and this addition would not suffice, without the farther circumstance of everlasting happiness as the reward. But such is not his meaning, nor is it easy to fix the meaning. He unites the two conditions--Human Happiness and the Will of the Deity--and holds them to coincide and to explain one another. Either of the two would be a sufficient definition of virtue; and he would add, as an explanatory proposition and a guide to practice, that the one may be taken as a clue to the other. In a double criterion like this, everything depends upon the manner of working it. By running from one of the tests to another at discretion, we may evade whatever is disagreeable to us in both. Book II., entitled MORAL OBLIGATION, is the full development of his views. Reciting various theories of moral right and wrong, he remarks, first, that they all ultimately coincide; in other words, all the theorists agree upon the same rules of duty--a remark to be received with allowances; and next, that they all leave the matter short; none provide an adequate _motive_ or inducement. [He omits to mention the theory of the Divine Will, which is partly his own theory]. In proceeding to supply this want, he asks first 'what is meant by being obliged to do a thing;' and answers, '_a violent motive resulting from the command of another_.' The motive must be violent, or have some degree of force to overcome reluctance or opposing tendencies. It must also result from the _command_ of another; not the mere offer of a gratuity by way of inducement. Such is the nature of Law; we should not obey the magistrate, unless rewards or punishments depended on our obedience; so neither should we, without the same reason, do what is right, or obey God. He then resumes the general question, under a concrete case, 'Why am I obliged to keep my word?' The answer accords with the above explanation;--Because I am urged to do so by a violent motive (namely, the rewards and punishments of a future life), resulting from the command of God. Private happiness is the motive, the will of God the rule. [Although not brought out in the present connexion, it is implied that the will of God intends the happiness of mankind, and is to be interpreted accordingly.]