You ask what it means for a man to do what is in him. Alexander of Hales answers as follows. "If we want to know what it means for one to do what is in him, let us first note that every man by nature possesses right reason. This uprightness of reason consists of a natural understanding of what is good. It is given to every man by the Creator, and by it every soul can know its origin, God, . . . It knows further that it should seek the good from its Creator, that all men should beg what they still lack from their origin. If a man acts in accordance with this innate knowledge and directs his will to him whom he knows to be his praiseworthy Creator, then he does what is in him. This is generally what it means for any man to do what is in him. The infidel in mortal sin, however, needs more light, for his faith is unformed, lacking in charity. But this unformed faith can still make two things clear to him: divine justice which damns those who are false and divine mercy which saves the righteous. Knowledge of the former creates fear, and knowledge of the latter hope. To fear God's justice and hope in his mercy is to do what is in one." So Alexander. From this we can now say that he does what is in him who, illumined by the light of natural reason or of faith, or of both, knows the baseness of sin, and having resolved to depart from it, desires the divine aid [i.e. grace] by which he can cleanse himself and cling to God his maker. To the one who does this God necesssarily grants grace - but by a necessity based on the immutability of his decisions, not on external coercion, as Alexander also declares.