The seven liberal arts do not adequately divide theoretical philosophy; but, as Hugh of St. Victor says, seven arts are grouped together (leaving out certain other ones), because those who wanted to learn philosophy were first instructed in them. And the reason why they are divided into the trivium and quadrivium is that “they are as it were paths (viae) introducing the quick mind to the secrets of philosophy.”
Thomas Aquinas cited in: Pierre Hyacinth Conway, Benedict M. Ashley (1959) The liberal arts in St. Thomas Aquinas. p. 8