Objection 1. It seems that goodness has not the aspect of a final cause, but rather of the other causes. For, as Dionysius says (Div. Nom. iv), "Goodness is praised as beauty." But beauty has the aspect of a formal cause. Therefore goodness has the aspect of a formal cause.
Objection 2. Further, goodness is self-diffusive; for Dionysius says (Div. Nom. iv) that goodness is that whereby all things subsist, and are. But to be self-giving implies the aspect of an efficient cause. Therefore goodness has the aspect of an efficient cause.
Objection 3. Further, Augustine says (De Doctr. Christ. i, 31) that "we exist because God is good." But we owe our existence to God as the efficient cause. Therefore goodness implies the aspect of an efficient cause.
On the contrary, The Philosopher says (Phys. ii) that "that is to be considered as the end and the good of other things, for the sake of which something is." Therefore goodness has the aspect of a final cause.
I answer that, Since goodness is that which all things desire, and since this has the aspect of an end, it is clear that goodness implies the aspect of an end. Nevertheless, the idea of goodness presupposes the idea of an efficient cause, and also of a formal cause. For we see that what is first in causing, is last in the thing caused. Fire, e.g. heats first of all before it reproduces the form of fire; though the heat in the fire follows from its substantial form. Now in causing, goodness and the end come first, both of which move the agent to act; secondly, the action of the agent moving to the form; thirdly, comes the form. Hence in that which is caused the converse ought to take place, so that there should be first, the form whereby it is a being; secondly, we consider in it its effective power, whereby it is perfect in being, for a thing is perfect when it can reproduce its like, as the Philosopher says (Meteor. iv); thirdly, there follows the formality of goodness which is the basic principle of its perfection.
Reply to Objection 1. Beauty and goodness in a thing are identical fundamentally; for they are based upon the same thing, namely, the form; and consequently goodness is praised as beauty. But they differ logically, for goodness properly relates to the appetite (goodness being what all things desire); and therefore it has the aspect of an end (the appetite being a kind of movement towards a thing). On the other hand, beauty relates to the cognitive faculty; for beautiful things are those which please when seen. Hence beauty consists in due proportion; for the senses delight in things duly proportioned, as in what is after their own kind--because even sense is a sort of reason, just as is every cognitive faculty. Now since knowledge is by assimilation, and similarity relates to form, beauty properly belongs to the nature of a formal cause.
Reply to Objection 2. Goodness is described as self-diffusive in the sense that an end is said to move.
Reply to Objection 3. He who has a will is said to be good, so far as he has a good will; because it is by our will that we employ whatever powers we may have. Hence a man is said to be good, not by his good understanding; but by his good will. Now the will relates to the end as to its proper object. Thus the saying, "we exist because God is good" has reference to the final cause.
Source: Summa Theologica (New Advent)