What kind of liberty is necessary to enable the will to acquire merit? Theologians answer by saying that it is _libertas contradictionis sive exercitii_. If I do a good deed which I am free to do or not to do, I perform a morally good and therefore meritorious work. As regards the _libertas specificationis_, (that freedom by which a person may act thus or otherwise, _e.g._ give alms to one applicant in preference to another, or mortify himself in this or that particular manner), there can be no doubt that, whatever the choice made, the action is always good and meritorious. However, theologians have excogitated a hypothetical case in which an action may be _physically_ free without being meritorious. It is when one is compelled to do a certain thing and is free only in so far as he is able to choose between two actions exactly equal in moral worth. This would be the case, for instance, if he had to pay a debt of ten dollars and were left free to pay it either in coin or in currency. The more common opinion is that in a case of this kind there would be a lack of that liberty which is necessary to render an act morally good and therefore meritorious.(1284) c) The third requisite of merit is actual grace. Its necessity is evident from the fact that, to be meritorious, an act must be supernatural and consequently cannot be performed without the aid of prevenient and coöperating grace.(1285) d) Merit further requires a supernatural motive, for the reason that every good work must be supernatural, both as regards object and circumstances (_ex obiecto et circumstantiis_), and the end for which it is performed (_ex fine_). In determining the necessary qualities of this motive, however, theologians differ widely.