Ask a Thomist

Aquinas and the Problem of Universals

I’ve heard that Aquinas solved the problem of universals and particulars by taking a middle ground? Honestly I don’t really know what that means nor do I know how he did it (and where it is in the summa). Please help. – Craig

St. Thomas certainly addressed the question in his philosophical and theological readings. That being said, there isn’t a question or even an article dedicated directly to the matter in the Summa Theologiae. The Summa was written as a course of theological formation for Dominicans preparing to become priests and confessors. Thus, it presumes that they would have had knowledge of the prerequisites (including philosophy). If you’re interested in reading St. Thomas on the matter, you might consult his De Ente et Essentia which is a short philosophical treatise that he composed at the beginning of his career. Alternately, you could look at any number of good introductions to his thought (or even philosophy more broadly) if you find the question especially compelling.

Essentially, the question can be expressed in the following manner: After having encountered something, why is it that upon my next encounter with something of that “kind” I recognize it to be such? Is there something universal that unites these particular experiences? Throughout the history of philosophy, a variety of answers have been given to the question. At the one extreme, you have the answer of Plato. In Plato’s estimation, there is a realm of the forms where these universals (“dogness,” “treeness,” “humanity,” etc.) exist apart from the world of sense in a rarefied and pure form. Everything that we encounter in this world below is but a pale shadow of or participation in one of these forms which imparts to things their intelligibility. On the other end of the spectrum, one finds a variety of modern thinkers who say that there is nothing that really and truly unites our experience of similar things except our associations. Either it’s a nominal connection (in name only) or logical (in thought only) or otherwise, but not really. St. Thomas falls between these positions, but closer to Plato. For St. Thomas, the forms don’t exist in some celestial sphere apart from the created world. Rather, forms exist in things. But, there are real kinds of forms which exist in distinct packets of matter. So, the form of dog is variously instantiated in different dogs, but there is an intelligible connection between those dogs because they participate/instantiate the form of dogness. So, when we encounter one dog and apprehend it as such, we abstract the form of dog and it takes up an intentional (or conceptual) existence in our mind. Then, when we encounter another dog and grasp the form of that one, we are able to refine our concept of dog and reason upon it. The intentional form (intelligible species) and the sense memory (phantasm) associated with it then becomes the instrument whereby we engage with material reality in subsequent encounters.


Fr. Gregory Pine, O.P. serves as the Assistant Director for Campus Outreach for the Thomistic Institute. Born and raised near Philadelphia, PA, he later attended the Franciscan University of Steubenville, studying mathematics and humanities. Upon graduating, he entered the Dominican Province of St. Joseph in 2010 and was ordained in 2016. “It was St. Thomas Aquinas who first introduced me to the Order, and by his prayers that I grew in knowledge and love of its saving mission and ultimately came to find my happiness in Order of Friars Preachers.”

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