From a consideration of the primacy of ethics in Dante’s The Banquet by Etienne Gilson in Dante the Philosopher (1948):
…the Crystaline heaven, or Primum Mobile, ordains by its motion the daily revolution of all the other heavens, a revolution that enables them to receive and transmit to the earth each day the efficacy of all their parts. If the revolution of the Primum Mobile ceased to make the other [eight] heavens go round, we should see but a faint part of them on earth and we should feel their influence but slightly. There would no longer be in the world any reproduction of living animals and plants, or any distinction of day or night; there would be no weeks, or months, or years, but the whole universe would be in disorder and the motion of the other heavens would be in vain: ‘And likewise, if moral philosophy ceased to be, the other sciences would for a while be eclipsed, there would be no survival of felicity, nor would life hold any happiness, and these sciences would have been formulated and discovered of old in vain. Whence it is very clear that this heaven is connected with moral plilosophy’ (Dante, The Banquet, II, 14).
The thesis which Dante here maintains is quite extraordinary for the Middle Ages. Taken literally, it amounts to the maintenance of the primacy of ethics over metaphysics, a doctrine which at any rate could not claim the authority of Aristotle and perhaps still less that of St. Thomas Aquinas. (105)
Why, then, instead of classifying the sciences according to the order of their absolute perfection, should we not classify them according to their increasing capacity for beatifying us? To do so means committing ourselves to place at the summit of the hierarchy not the most divine of all sciences, but the most human of all sciences. Not metaphysics, but ethics. (107)