In a long post about a lot of unrelated things, Joe Carter includes a quote from Peter van Inwagen's God, Knowledge, & Mystery about philosophers and theologians in terms of citing authorities:
One advantage philosophers bring to theology is that they know too much about philosophy to be overly impressed by the fact that a particular philosopher has said this or that. Philosophers of the present day know what Thomas Aquinas and Professor Bultmann did not know: that no philosopher is an authority. Philosophers know that if you want to pronounce on, say, the project of natural theology, you cannot simply appeal to what Kant has established about natural theology. You cannot do this for the very good reason that Kant has established nothing about natural theology. Kant has only offered arguments, and the cogency of these arguments can be (and is daily) disputed.
It's been a long time since I read that book, and I don't remember this quote. It was at the very beginning of my graduate studies, almost a decade ago. So seeing this quote now, with all I've learned since, makes me cringe in ways I would not have thought to do so when I read that section of the book.
Thomas Aquinas would no more have assumed that you could cite a famous philosopher as an authority in this way than any philosopher today would, and anyone who thinks he would knows very little about Aquinas, with all due respect to van Inwagen. Aquinas' main methodology in his largest and most significant work is to state a question, present objections to his view, some of which are from previous figures, a biblical text, or a contemporary figure, state his own view, often citing a similar authority but not always, and then argue for his view before finally responding to the objections. He did not cite authorities as if that proved anything. He gives reasons. He did not take authorities to be a sign of the truth of anything, since the authorities appear just as much in the objections he's responding to as they do in the statement of his own view.
I don't know about Bultmann, and I don't know which contemporary theologians he has in mind (although the ones I know give actual arguments and don't generally take famous figures as substitutes), but it takes someone very unfamiliar with a giant of the tradition to say this about Aquinas, and it disappoints me to find one of the top philosophers of our day saying it of him.