Necesse est quod omnia quae homo appetit, appetat propter ultimum finem, quia quidquid homo appetit, appetit sub ratione boni.
Man must, of necessity, desire all, whatsoever he desires, for the last end, because whatever man desires, he desires it under the formal aspect of good.
Quod quidem si non appetitur ut bonum perfectum, quod est ultimus finis, necesse est ut appetatur ut tendens in bonum perfectum, quia semper inchoatio alicuius ordinatur ad consummationem ipsius; sicut patet tam in his quae fiunt a natura, quam in his quae fiunt ab arte. Et ideo omnis inchoatio perfectionis ordinatur in perfectionem consummatam, quae est per ultimum finem.
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 of nature and of art. Wherefore every beginning of perfection is ordained to complete perfection which is achieved through the last end.
Secundo, quia ultimus finis hoc modo se habet in movendo appetitum, sicut se habet in aliis motionibus primum movens. Manifestum est autem quod causae secundae moventes non movent nisi secundum quod moventur a primo movente. Unde secunda appetibilia non movent appetitum nisi in ordine ad primum appetibile, quod est ultimus finis.
Secondly, because the last end stands in the same relation in moving the appetite, as the first mover in other movements. Now it is clear that secondary moving causes do not move save inasmuch as they are moved by the first mover. Therefore secondary objects of the appetite do not move the appetite, except as ordained to the first object of the appetite, which is the last end.
Non oportet ut semper aliquis cogitet de ultimo fine, quandocumque aliquid appetit vel operatur, sed virtus primae intentionis, quae est respectu ultimi finis, manet in quolibet appetitu cuiuscumque rei, etiam si de ultimo fine actu non cogitetur. Sicut non oportet quod qui vadit per viam, in quolibet passu cogitet de fine.
One need not always be thinking of the last end, whenever one desires or does something, but the power of the first intention, which is in respect of the last end, remains in every desire directed to any object whatever, even though one's thoughts be not actually directed to the last end. Thus while walking along the road one needs not to be thinking of the end at every step.
Augustinus, XIX de Civ. Dei, "illud est finis boni nostri, propter quod amantur cetera, illud autem propter seipsum".
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."