"a science can be higher than another in two ways, either by reason of its subject, . . . or by reason of its mode of knowing, and thus theology is below the knowledge that is God's. For we imperfectly know what he knows perfectly, and just as a science subalternated to a higher presupposes certain things and proceeds from these as from principles, so theology presupposes the articles of faith which are proved infallibly in God's knowledge, believes them and through them proceeds to prove what follows from the articles. Thus theology is as it were a science subalternated to the divine science from which it receives its principles."
Pretty basic Aquinas, but always a breath of fresh air wherever re-encountered. Thomas Aquinas, Commentary on the Sentences, q. 1 a. 3 qc. 2 ad 1 (Vivès edition); Thomas Aquinas: selected writings, ed. and trans. Ralph McInerny (London: Penguin Books, 1998), 61-62. According to Enrique Alarcón, who cites pp. 106 ff., 139 ff., and 159 of the authoritative new Leonine edition edited by Oliva (Les débuts de l'enseignement de Thomas d'Aquin et sa conception de la 'sacra doctrina': édition du prologue de son 'Commentaire des Sentences' de Pierre Lombard (Paris: J. Vrin, 2006)), to which I don't have immediate access, this is part of a later, optional addition to ad 2 that some thirty manuscripts (and the Vivès edition) inserted mistakenly after ad 1. Because it doesn't yet have permission to use the superior new Leonine edition, Corpus Thomisticum (http://www.corpusthomisticum.org/snp0001.html#37) follows for now the Parma edition. (All of that in a gracious reply to me dated 29 July 2008.)