N.B.: You will not understand this post unless you know about the concepts of act and potency; for my attempt at explaining them, you can see Aristotelian Metaphysics, Pt. 1: Act and Potency. Note that my earlier post on per se vs. per accidens causation (available here) was intended as a supplement, NOT officially part of this series.
Now it’s time to derive the implications of act and potency.
The most obvious implication of act and potency is the efficient cause. Recall that, as mentioned in the first part, the outcome of any change exists potentially before the change. Well, how does that potency become actual? It can’t make itself actual, because nothing in potency can do anything. If it could, then the potential fire in all of our unlit matches would be wreaking havoc.
So a potency cannot raise itself to act. Nor can any other potency raise another potency to act. Therefore, a potency must be actualized by something else that is already actual. This we call the efficient cause. This is the cause we usually have in mind when we use the unqualified word “cause” in modern English. So e.g. the front car of a train is the efficient cause of the whole train moving, electricity running through a filament is the efficient cause of a light bulb giving off light, air blowing through the vocal folds is the efficient cause of a person’s voice, and a sculptor’s chiseling is the efficient cause of a statue coming into being.
Incidentally, that last step in the derivation of the efficient cause is an important presupposition in the First Mover argument: Any potency that is raised to act, must be actualized by something that is already in act. Most people get this wrong; you usually encounter this axiom phrased as, “Everything has a cause.” People then use this misformulation to argue for the existence of God, which leads to a blatant contradiction between the conclusion and the premise. Neither Aristotle nor Thomas Aquinas ever made such an argument. As Michael “TOF” Flynn says in his series of posts on the First Mover argument, “The Argument from Motion may be wrong, but it is not stupidly wrong.”
The next, less obvious implication is the final cause. We see that the things around us have many different potencies. When an efficient cause actualizes a potency of something, it does not actualize all of the latter’s potencies; that would be impossible, because any given thing will have contrary potencies, e.g. the potential to be blue and the potential to be red, or the potential to be freezing cold and the potential to be boiling hot.
Nor is the potency to be actualized selected at random. Rather, we see that the potency actualized depends largely on the efficient cause in question, and to a lesser extent on the subject that is being changed. Thus e.g. taking a fruit and putting it in a blender makes one result (a smoothie), while taking the same fruit, pulverizing it into mush, and putting it in a candy gives another result (Skittles (TM)). Here, we start with the same object, but end up with different results because the action done to it was different.
So an efficient cause “chooses,” so to speak, a single potency to actualize (or, more commonly, a single range of potencies to actualize, with the final outcome being determined by the thing that is being changed). This particular outcome (or range of outcomes) that a cause is naturally directed toward is what we call the final cause. So e.g. the final cause of striking a match is the starting of a fire, the final cause of bowing a violin is the generation of music, the final cause of gravity pulling on something is the downward acceleration of that thing, etc.
Notice that our examples of final causality and efficient causality are interchangeable, because every instance of efficient causation is also an instance of final causation, and as far as physical processes are concerned, every instance of final causation is also an instance of efficient causation. So the final cause of a train car pulling on the other train cars is the motion of the entire train, the final cause of electricity running through a filament is the generation of light, the final cause of air blowing through the vocal folds is the generation of the voice, and the final cause of a sculptor’s chiseling is the coming into being of a statue. Similarly, the efficient cause of the starting of a fire is the striking of the match, the efficient cause of the generation of music is the bowing of the violin, and the efficient cause of the downward acceleration of objects is gravity pulling on those objects.
Note as well that there is a close relationship between final cause and purpose. For one thing, it is because we are capable of knowing the final causes of natural objects that we are then able to take advantage of them and order them to our own ends; thus e.g. we can take advantage of the wind’s tendency to push on things in order to generate electricity. For another thing, since our conscious purpose is the result that we order our actions to achieve, conscious purpose is essentially a subset of final causes; our goal is the final cause of our actions. In this sense, I guess not every instance of final causation has to be an instance of efficient causation. However, much, perhaps most final causation is unconscious. Gravity does not pull on things because it (he?) wants them to accelerate.
It might seem counterintuitive to think of the final cause as a “cause,” since on the face of it it looks more like a result than a cause. But think of it this way. What would it mean for something to be changing, but not into anything in particular? Clearly this is absurd; if a thing wasn’t changing into anything in particular, then it wouldn’t be changing at all. It would be like a thing existing without being anything in particular. To change is to change into something, just as to be is to be something. In this sense, change depends on its endpoint if it is to occur at all. The endpoint is what gives the change its “identity,” so to speak.
Or again, the only kinds of changes I can think of that might credibly be called changing into nothing in particular would be changing into every possible thing, which is absurd, and fading out of existence. And even these changes have a kind of goal: in the former case it would be everything, and in the latter it would be non-existence. So change can’t even be conceived of without being “aimed” at some particular goal.
Possibly the best evidence that people actually do (consciously or not) think in terms of final causes is that we can still tell what the final cause of a given thing is even if it fails to achieve that final cause. So e.g. if you strike a match and no fire comes out, you wouldn’t say that, oh, I guess that particular thing I just tried to strike wasn’t actually a match, then. No, the natural inference is that it was a match, and it was supposed to make fire, but some kind of deficiency or interference prevented the normal result―maybe you didn’t strike it hard enough, or maybe the match was wet, for example. This tells us that the final cause is an intrinsic aspect of things, regardless of whether they actually achieve that result or not. It also rules out the “law of nature” interpretation of the regularity of causes. There’s no law that every match must catch fire when struck, nor does that actually happen in practice. And yet we still have this notion that striking a match is “supposed” to make it catch fire. If our understanding of causality were based on laws of regularity, then the moment we witnessed a match fail to catch fire for the first time, either A) we would have to conclude that the object we just attempted to strike was not a match at all, or B) our entire understanding of matches that we had built up until then would fall apart. We would have to change our conception from “Matches catch fire” to “Some matches catch fire,” or “Matches catch fire 90% of the time.” But neither of these options is what happens in practice; nobody has any difficulty coping with duds, and even after encountering them, people still say “Matches catch fire” without any qualms. This is because “Matches catch fire” is not a statement of regularity, but a statement of directedness―in other words, final causality.
By contrast, if you use a computer mouse and it doesn’t catch fire, well… now that just makes sense, doesn’t it? That’s because using a mouse doesn’t have catching fire as a final cause. This case is fundamentally different from the match case; here there is no expectation for the mouse to catch fire to begin with, and therefore no existential crisis when the mouse fails to catch fire.
Final causes are particularly evident in physics, where we talk about how e.g. so many newtons of force would cause a mass of so many kilograms to accelerate at a rate of so many meters per second per second. It doesn’t matter whether the force ever does accelerate that much mass at that rate; simply having that magnitude means that by nature that force would cause such a mass to accelerate at that rate. Here, the acceleration is the final cause of the force. Even if the force is counteracted so that it never actually accelerates something, or it accelerates something at a slower rate than it would otherwise, we still understand that the force is “supposed” to accelerate something at a certain rate. So if you dismissed the match example above as being a pragmatic aspect of the way we think, not a true part of reality, then try taking the above paragraph and changing it so that instead of matches catching fire, it talked about forces causing things to accelerate; I’ll wager that the argument still makes sense. Since forces and acceleration are definitely not something humans just invented, the fact that it’s possible for us to think about forces the same way we do about matches, and that this way of thinking still works in that context, seems to me like strong evidence for real, not merely conceptual or pragmatic, final causality.
In any case, whether you like to call it a cause or not, it’s impossible to make sense of both the regularity of efficient causes, and our ability to tell apart cases of deficiency (like the match dud) from cases of simply not happening (like the computer mouse), without either implicitly or explicitly assuming that every cause inherently “leads” or “points” toward a definite result regardless of whether it actually achieves that result or not.
There are two other causes left to discuss, but I think it might be easier to explain them after going over substance and accident. So rather than go over those here, I’ll leave them for part 3.