Thomas Aquinas: A Beginner’s Guide (Feser)

Feser, Edward. Thomas Aquinas: A Beginner’s Guide.

I do not know if I would call this a “beginner’s guide.”  Parts of it deal with discussions in current analytical philosophy, and some of these discussions would discourage the beginner.  It is an indispensable guide, though. Edward Feser highlights the key elements in Thomas’s thought.  You cannot go wrong in interpreting Thomas with Feser as your guide.

Thomas’s views on causality are well-known, so we will only focus on the basics.  Final causality for Thomas is directional. It is always pointing.


Not surprisingly, we get a good discussion of the essence/existence distinction. For God, essence and existence are the same.  There is not a genus called “God” to which one could apply the category existence.  This makes sense at the creaturely level.  I know what the essence of a unicorn is.  Whether it exists or not, I have a clear idea of its essence. For existent things, their essences have to be conjoined with their existences. Even the angels who are pure form are not identical with their existence. They are an essence conjoined with the act of existence.

Feser gives us a good handle on the act/potency distinction.  God is pure act with no unrealized potencies.   The more act a being has, the higher on the chain of reality it is.  God is at the top.  Prime matter, which is only unrealized potency, is at the bottom.  Similarly, motion is simply a change from a potency to an act.

Natural Theology

The greatest harm ever done to Thomas was by philosophy of religion anthologies.  Thomas never intended for his 5 Ways to be read in isolation from his larger project.  I suppose that cannot be helped, though. Feser helps us avoid the pitfalls of misinterpreting Thomas.  We will focus on his argument from motion.  There are two types of causal serieses. There is a causal series per accidens.  This is where one sequence follows another.  Some apologists argue that every effect has a cause and God must be the ultimate cause.  True, but there are some difficulties. In a causal series per accidens one has trouble transcending that series.  

Thomas’s solution, though, is different. There is another type of causal series. It is a causal series per se. If the former is sequential, this is hierarchical. Every potency is actualized by a prior act.  This allows Thomas to evade the charge that since philosophy cannot disprove the eternity of the universe, then it does not need God as a cause.  Thomas answers that is true for a per accidens series, not a per se one.  Even if the universe were eternal, the potencies in it would need to be actualized.


Thomas is a dualist, but he is not a Cartesian or Platonist.  Feser explains that “soul” for Aquinas simply means the form of a person. It in-forms the matter. For Plato or Descartes, a soul was literally a ghost in the machine, with all the problems that entails. Thomas does not need that ghost.


Natural law is important for Thomas, but not that important.  He devotes surprisingly little space to it.  What is more important and of higher priority is the Good.  Natural law does not make a lot of sense without a previous orientation to the Good.  Moderns since David Hume have attacked natural law for committing the naturalistic fallacy, of deriving an ought from an is or value from facts. That’s a very sharp criticism, but it only works if nominalism is true and all we have is a mechanistic universe.  Thomas would not have understood the fact-value problem because medieval man did not think in terms of value, but of the Good, and the Good is already inherent in reality.


This is an excellent treatment of Thomas’s thoughts. One will not misinterpret Thomas with Feser as a guide. It’s not a beginner’s treatment, though.

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