In a previous post I quoted Fergus Kerr who noted that Aquinas’s epistemology presupposed theology. Because the Christian God created the world and creatures in order for them both to interact on an essential level the world can be known by man. Norman Kretzmann’s article “Infallibility, Error, and Ignorance” (in the 1992 Supplementary Volume 17 of the Canadian Journal of Philosophy) is the most thorough and clear treatment of Aquinas’s epistemology that I have come across. He places the Thomistic theory of knowledge within the camp of reliabilism – that the mind is a reliable tool for discovering truth outside of the mind. He notes that Aquinas did not cease to follow Aristotle in his philosophy of knowledge but:
For Aquinas, the theological component of his theistic reliabilism naturally comes first […] The component of cognitive reliability in theistic reliabilism could reasonably be said to be implied by a few basic theological doctrines which Aquinas of course argued for, quite independently of their implications for epistemology: God, the creator, is omniscient, omnipotent, and perfectly good; and part of his purpose in creating is the manifestation of himself to rational creatures. From those central doctrines alone it seems to follow that skepticism is frivolous – that human beings must have been created with reliable access to created reality and with reliable faculties for the processing of the reliably acquired data. (Kretzmann, pp. 162, 163)
These assertions on Kretzmann’s part are immediately backed up by Aquinas’s own language:
The immediate purpose of the human body is the rational soul and its operations, since matter is for the sake of the form, and instruments are for the sake of the agent’s operations. I maintain, therefore, that God designed the human body in the pattern best suited to that form and those operations. (ST Ia.91.3c)
Therefore, because God designed the human body with the rational soul as an instrument for comprehension then truths outside of the mind can be known, and thus man can have infallible knowledge. Coming from a Reformed perspective, and Van Tilian at that, this relationship between theology and epistemology in St. Thomas, as a friend of mine responded to me the other day, sounds “presuppositional”. I’d recommend this article (although it may be hard to find) by Kretzmann to anyone interested, especially newbies like myself.