Roger Olson says that Thomas used Aristotle as an authority in sacra doctrina. Though this is true there is a caveat that needs to be given for those with a natural distaste for philosophy and everything pagan. Philosophers can be called authoritative only when used contra gentiles. Thomas confirms:

Insofar as sacred doctrine uses philosophical teachings in its own interest, it does not welcome them because of the authority of their authors but on account of the reasonableness of what they say. What is well said it takes; the rest it rejects.  But when it uses them to refute other writers, it does so because they are accepted as authorities by those who are refuted, for the witness of opponents carries greater weight. (Expositio super librum Boethii de Trinitate, Q. 2, a. 3.)