“Causa efficiens et finis sibi correspondent invicem, quia efficiens est principium motus, finis autem terminus. Et similiter materia et forma: nam forma dat esse, materia autem recipit. Est igitur efficiens causa finis, finis autem causa efficientis. Efficiens est causa finis quantum ad esse, quidem, quia movendo perducit efficiens ad hoc, quod sit finis. Finis autem est causa efficientis non quantum ad esse sed quantum ad rationem causalitatis. Nam efficiens est causa in quantum agit; non autem agit nisi causa [gratia] finis. Unde ex fine habet suam causalitatem efficiens.”—St. Thomas, In Metaph., v., 2.
“Sciendum quod licet finis sit ultimus in esse in quibusdam, in causalitate tamen est prior semper, unde dicitur causa causarum, quia est causa causalitatis in omnibus causis. Est enim causa causalitatis efficientis, ut jam dictum est. Efficiens autem est causa causalitatis et materiae et formae.”—ibid., lect. 3.
“Natura nihil aliud est quam ratio cujusdam artis, scilicet divinae, indita rebus qua ipsae res moventur ad finem determinatum; sicut si artifex factor navis posset lignis tribuere quod ex seipsis moverentur ad navis formam inducendam.”—In II Phys., lect. 14.
“Omnia naturalia, in ea quae eis conveniunt, sunt inclinata, habentia in seipsis aliquod inclinationis principium, ratione cujus eorum inclinatio naturalis est, ita ut quodammodo ipsa vadant, et non solum ducantur in fines debitos.”—De Veritate, q. xxii., art. 7.
... Among themselves all things
Have order; and from hence the form, which makes
The universe resemble God. In this
The higher creatures see the printed steps
Of that eternal worth, which is the end
Whither the line is drawn. All natures lean
In this their order, diversely, some more,
Some less approaching to their primal source.
Thus they to different havens are moved on
Through the vast sea of being, and each one
With instinct giv'n, that bears it in its course;
This to the lunar sphere directs the fire,
This prompts the hearts of mortal animals,
This the brute earth together knits and binds.
Nor only creatures, void of intellect,
Are aim'd at by this bow; but even those
That have intelligence and love, are pierced.
That Providence, who so well orders all,
With her own light makes ever calm the heaven,
In which the substance that hath greatest speed
Is turned: and thither now, as to our seat
Predestin'd, we are carried by the force
Of that strong cord, that never looses dart,
But at fair aim and glad ...
—Dante, Paradiso, Cant. i. (tr. by Cary).