Four Causes and Five Ways

Noting parallels and correlations can be philosophically illuminating and pedagogically useful.  For example, students of Aristotelian-Thomistic (A-T) philosophy are familiar with how soul is to body as form is to matter as act is to potency.  So here’s a half-baked thought about some possible correlations between Aquinas’s most general metaphysical concepts, on the one hand, and his arguments for God’s existence on the other.  It is well known that Aquinas’s Second Way of arguing for God’s existence is concerned with efficient causation, and his Fifth Way with final causation.  But are there further such parallels to be drawn?  Does each of the Aristotelian Four Causes have some special relationship to one of the Five Ways?   Perhaps so, and perhaps there are yet other correlations to be found between some other key notions in the overall A-T framework.

Consider first the most general concepts of A-T metaphysics and their interrelations.  As I suggest in Scholastic Metaphysics, the entire edifice is grounded in the distinction between act and potency (or actuality and potentiality), which I spell out in chapter 1 of that book (after the prolegomenon of chapter 0, which refutes scientism etc.).  Chapter 2 then shows how, from the theory of act and potency, we can derive the notions of efficient causality and final causality.  Efficient causality involves the actualization of potency.  Final causality enters the picture insofar as a potency is always directed toward a certain outcome or range of outcomes as toward an end. 

Chapter 3 goes on to show how form and matter, which are the main constituents of a physical substance, also follow from the theory of act and potency.  Prime matter, which is the material cause of a physical substance, is the pure potentiality for the reception of form.  Substantial form, which is the formal cause of a material substance, is what actualizes prime matter.  Chapter 4 then shows how the distinction between essence and existence, which (unlike the distinction between form and matter) applies to immaterial substances as well as to physical substances, also follows from the theory of act and potency.  The essence of a thing is, by itself, merely potential; existence is what actualizes that potential so that we have a concrete substance. 

So, we have the following six fundamental A-T concepts: the act/potency distinction; efficient cause; final cause; formal cause; material cause; the essence/existence distinction. 

Now consider Aquinas’s arguments for God’s existence (which I discuss and defend in detail in chapter 3 of Aquinas).  The first of the Five Ways is the argument from motion or change to a divine Unmoved Mover.  The Second Way is the argument from the existence of series of efficient causes to a divine Uncaused Cause.  The Third Way begins from the fact that things come into being and pass away and argues for an absolutely Necessary Being.  The Fourth Way argues from the degrees of perfection to be found in things to the existence of a Most Perfect Being.  The Fifth Way argues from the existence of final causes to a divine Supreme Intelligence which directs things to their ends.

Aquinas also famously presents, in On Being and Essence, an argument from the existence of things in which there is a distinction between essence and existence to a divine cause which is Subsistent Being Itself.  This is sometimes called “the existential proof” and its relationship to the Five Ways is unclear.  In Aquinas I suggested that the argument corresponds to the Second Way, but that is certainly not obvious, and not everyone would agree with the suggestion.  As what I say below indicates, a case could certainly be made for reading it another way.

Hence, we (arguably) have in Aquinas at least six different arguments for God’s existence: the Five Ways plus the “existential proof.”

Perhaps you see where this is going.  Is there an interesting correlation between the six fundamental A-T metaphysical notions, on the one hand, and the six arguments for God’s existence on the other?  Arguably so.

Motion or change entails, for A-T, the actualization of potency, so the First Way naturally correlates with the theory of act and potency.  The Second Way, as already noted, naturally correlates with the notion of efficient causality. 

What about the Third Way?  Well, the way it gets to an absolutely Necessary Being is by beginning with things that are the opposite of that -- that is to say, with things that are generated and corrupted, which come into being and pass away.  Note that (contrary to what many modern discussions of the Third Way imply) these are not exactly the same things as “contingent beings” in the contemporary sense of that term.  When contemporary philosophers talk about a “contingent” thing, what they mean is a thing which might in principle not exist.  Angels would in this sense be contingent, since although they are immaterial substances and thus incorruptible, they could have failed to exist had God not created them.  For Aquinas, by contrast, angels are necessary rather than contingent, precisely because they are incorruptible in the sense that nothing in the natural order of things can destroy them.  What differentiates them from God is that they still have to be created and sustained in being by God, so that they have necessity in only a derivative rather than absolute way.  Obviously, then -- and as some critics of the Third Way do not realize, leading them to get the argument seriously wrong -- Aquinas does not use the word “necessary” the way contemporary philosophers do.  And to start with something like an angel would for him therefore not be a good way to start an argument like the Third Way.

What he starts with are things that are material and thus corruptible in a way immaterial substances are not.  Hence the Third Way plausibly correlates with the notion of material cause.  That is to say, just as the First Way essentially begins with the notion of act and potency and works to God as the purely actual actualizer of potency, and the Second Way begins with the notion of efficient cause and works to God as the source of all merely derivative efficient causal power, the Third Way essentially begins with the corruptibility entailed by the notion of material cause and works to God as what is absolutely incorruptible and thus necessary in the strongest possible sense.

The Fourth Way is famously the most Platonic-sounding of the Five Ways.  Aquinas’s account of how what has goodness in only a limited way participates in that which is Goodness Itself, that which has being in only a limited way participates in that which is Being Itself, etc. calls to mind Plato’s account of how things are what they are because they participate in the Forms.  Of course, Aquinas is an Aristotelian rather than a Platonist -- and thus has an Aristotelian rather than Platonic conception of form -- and (as I argue in Aquinas) what are in view in the Fourth Way are, specifically, what the medievals called the Transcendentals (being, goodness, truth, etc.), and not just any old thing for which Plato thinks there is a Form.  Still, there is arguably a special correlation between the Fourth Way and the notion of formal causation. 

The Fifth Way, as already noted, obviously correlates with the notion of final causality.  And the “existential proof” obviously correlates with the distinction between essence and existence.  If the existential proof really is (contrary to what I suggested in Aquinas) a distinct argument from the Second Way, the basis of the distinction might be this: While both arguments are concerned with explaining the existence of things and both arrive at God as the ultimate explanation of their existence, the manner of approach is different in each case.  The Second Way approaches the issue by way of the notion of the efficient causation of a thing’s existence; the existential proof approaches the issue by way of the notion of a thing’s essence/existence composition.

If all of this is correct, then the idea is that from each of the six basic explanatory notions, we can work to God as ultimate explanation.  And the correlations would, again and in summary, be as follows:

Act/potency                 →        First Way

Efficient cause              →        Second Way

Material cause             →        Third Way

Formal cause               →        Fourth Way

Final cause                   →        Fifth Way

Essence/existence        →        Existential proof

Again, though, I present this as at most half-baked.  Perhaps further reflection would complete the baking process and give us a well worked out and defensible set of correlations along these lines.  But perhaps it would instead result in somewhat different or somewhat looser correlations, or show that only the more obvious correlations (e.g. between the Second Way and efficient causation, the Fifth Way and final causation) are really defensible.