The third reason is because, since voluntary actions receive their species from the end, as stated above (A. 3), they must needs receive their genus from the last end, which is common to them all:  just as natural things are placed in a genus according to a common form.  Since, then, all things that can be desired by the will, belong, as such, to one genus, the last end must needs be one.  And all the more because in every genus there is one first principle; and the last end has the nature of a first principle, as stated above.  Now as the last end of man, simply as man, is to the whole human race, so is the last end of any individual man to that individual.  Therefore, just as of all men there is naturally one last end, so the will of an individual man must be fixed on one last end.

Reply Obj. 1:  All these several objects were considered as one perfect good resulting therefrom, by those who placed in them the last end.

Reply Obj. 2:  Although it is possible to find several things which are not in opposition to one another, yet it is contrary to a thing’s perfect good, that anything besides be required for that thing’s perfection.

Reply Obj. 3:  The power of the will does not extend to making opposites exist at the same time.  Which would be the case were it to tend to several diverse objects as last ends, as has been shown above (ad 2). ________________________

SIXTH ARTICLE [I-II, Q. 1, Art. 6]

Whether Man Wills All, Whatsoever He Wills, for the Last End?

Objection 1:  It would seem that man does not will all, whatsoever he wills, for the last end.  For things ordained to the last end are said to be serious matter, as being useful.  But jests are foreign to serious matter.  Therefore what man does in jest, he ordains not to the last end.

Obj. 2:  Further, the Philosopher says at the beginning of his Metaphysics (i. 2) that speculative science is sought for its own sake.  Now it cannot be said that each speculative science is the last end.  Therefore man does not desire all, whatsoever he desires, for the last end.

Obj. 3:  Further, whosoever ordains something to an end, thinks of that end.  But man does not always think of the last end in all that he desires or does.  Therefore man neither desires nor does all for the last end.

On the contrary, Augustine says (De Civ.  Dei xix, 1):  “That is the end of our good, for the sake of which we love other things, whereas we love it for its own sake.”

I answer that, Man must, of necessity, desire all, whatsoever he desires, for the last end.  This is evident for two reasons.  First, because whatever man desires, he desires it under the aspect of good.  And if he desire it, not as his perfect good, which is the last end, he must, of necessity, desire it as tending to the perfect good, because the beginning of anything is always ordained to its completion; as is clearly the case in effects both