Part — Wouters, Manual of Moral Theology
Dissertation I. On the End in General
I. Notion of end. An end is said to be: that for the sake of which something is done, or that for the sake of which an agent operates, or that which, by exciting the appetite of the one about to operate, draws him to acting. Now the appetite is drawn only by an apprehended good. Hence good and end, although they differ in formal concept, materially fall into the same thing. That is, one and the same thing is called a good insofar as it is fitting to the appetite; it is called an end insofar as, through that fittingness, it draws to acting.
Good, by reason of appetibility, is distinguished as threefold: honorable, delectable, and useful. The honorable is that which is conformable to the rules of morals; the delectable, that which is apt to satisfy the appetite; the useful, that which is apt for attaining some other good. Now since an end is that which by its goodness moves one to acting, a useful good as such does not have the character of an end but only of a means (St. Thomas, I, q. 5, a. 6, ad 2); for that which is chosen by reason of another is called a means. Thus, for example, victory is the end of those fighting, while the fight is the means.
II. Division of end. End is distinguished:
Into the end of the work and the end of the worker. The end of the work, or the intrinsic end, is the end to which the work by its nature is ordered. The end of the worker is the end which the worker intends in acting, whether it is the end of the work itself or some other end. Thus in almsgiving the end of the work is the relief of the poor person; the end of the worker can be the relief of the poor person, or vainglory, or something else (cf. St. Thomas, II-II, q. 141, a. 6, ad 1).
Into the end which, the end for whom, and the end by which. The end which is the very good that is intended; the end for whom is the person for whom the good is desired; the end by which is the very possession or acquisition of the intended good. Thus health is the end which, the sick person is the end for whom, and the acquisition of health is the end by which intended by the physician.1
Into the primary end and the secondary end. The primary or principal end is the one intended by the worker in such a way that, if it were lacking, he would not act, and for its sake he would act even if other ends were lacking. The secondary end is the one intended in such a way that without it the action would nevertheless be placed.
Into the final end and the intermediate end. The final end is the one intended only by reason of itself, and therefore not referred to another end. An intermediate end is said to be one which is indeed intended by reason of itself, but with a relation or subordination to a further end.
Into a natural end and a supernatural end, according as it can be attained by natural means or - as with the beatific vision - only by a supernatural means.
1 The end which and the end by which, for example health and its acquisition, likewise the end which and the end for whom, for example health and the sick person for whom health is desired, should not be taken as simply several ends, but rather as two quasi-parts of one total end (Billuart, same place, article 1).