Aquinas 101: Lesson Eleven

Saint Thomas Aquinas by Carlo Crivelli, downloaded from Wikipedia

Lesson 11: Act and Potency

The video (which is done by Fr. James Brent, OP) is very brief. And that was a common complaint in the comments at YouTube. But it was a good introduction to act and potency, and Fr. Brent talked about the ultimate cause of all change being an unmoved mover which we call God.

In the selected readings, I think Feser's description of the actualization of potency is helpful:

If the ball is to become soft and gooey, it can't be the actual gooeyness itself that causes this, since it doesn't yet exist. But that the gooeyness is non-existent is not (as Parmenides assumed) the end of the story, for a potential or potency for gooeyness does exist in the ball, and this, together with some external influence (such as heat) that actualizes that potential--or, as the Scholastics would put it, which reduces the potency to act--suffices to show how the change can occur. Change just is the realization of some potentiality; or as Aquinas puts it, 'motion is the actuality of a being in potency' (In Meta IX.1.1770).

The audio lecture, "Principles of Nature" by Fr. James Brent, OP, puts act and potency within the context of philosophy of nature. It's a very detailed lecture which may be difficult to absorb, not due to any fault of Fr. Brent's exposition, but rather because there is so much to take in. And I wonder if I can summarize in any way except by providing a rough outline.

At the beginning, Fr. Brent suggests Aquinas' summary of Aristotle in Principles of Nature. I can see something of the outline of Fr. Brent's lecture but the language of Aquinas may not be accessible to modern readers. Indeed, Fr. Brent takes care to point out that modern science and Aristotle's philosophy of nature are two different modes of analysis: the modern is analysis by elements (what things are made of) and the philosophy of nature is analysis by principles.

A. Aristotle has to deal with the problem of change:

1. some things change (this is the introduction of matter being the principle of potency in things)
   
2. some things change without ceasing to be what they are (this is the introduction of form as being the principle of act in things)
   There are 4 types of change (the first three are accidental changes)
   
   • quality
   • quantity
   • place
   • substantial change (something coming to be or passing away)
     
3. so then, some things come to be and pass away
4.  Nothing comes from nothing
   

This is the rational for potency (1), composition of substance and accident (2), and affirming continuity in nature (3 and 4).

The main principle for Aristotle is hylomorphism - all things of nature are composed of matter and form.

There are two levels of change which reveal two levels of composition

1.  Accidental change -- substance and accident
2.  Substantial change -- substantial form and primary matter

 A definition of change is given: actualization of what is in potential insofar as it is in potential -OR- potency becoming actual.

 B. The causes in nature

1. material - that out of which a thing is made
   
2. formal - that which makes a thing to be what it is
   
3. efficient (or agent) - that which brings the thing about (into being, source of motion, or rest)
   
4. final - that for the sake of which a thing is or comes to be (this is critical for Aristotle)

 Fr. Brent introduces two principles at this point

1. Whatever comes to be has an efficient cause
2. All agents act for the sake of an end
   

At the end, Fr Brent restates the two levels of analysis:

1. broadest, most general principles of nature and elaborating the essences of natural things (analysis by principles)
   
2. highly specific, highly detailed matters, a lot of it is regarding their accidental features (analysis by elements).

One of the good things about these lectures is that we'll be seeing these terms again and again. And so hopefully, one will be able to understand Thomistic and Aristotelian philosophy and embrace it.