Can a thing have more than one final cause?

Question

I have not been able to find anything on the Internet that answers this question. I also haven't been able to think of anything that has more than one final cause, as defined by Aristotle.

For example: Imagine a car. Their are many things they can be used for: driving around the countryside, hauling things to and fro, bringing your kid to school in the morning, etc. But it was built for one purpose: to transport anything that needs to be transported, for one reason or another.

Another example: Imagine a knife. Again, there are many things they can be used for: chopping onions, cutting animals open for food, etc. But it was made for one purpose: to cut things.

Considering these examples, it seems that a thing cannot have more than one final cause. Is this true?

Answer 1

Aristotle's Physics ch. 7 (198^a24-25) might help:

…the causes being four…

1. the matter [material cause],

2. the form [formal cause],

3. the mover [efficient or agent cause],

4. ‘that for the sake of which’ [final cause].

The last three often coincide; for the ‘what’ and ‘that for the sake of which’ are one, while the primary source of motion is the same in species as these (for man generates man)…

St. Thomas Aquinas commentates on this in In libros Physicorum lib. 2 lec. 11:

242. He [Aristotle] says, therefore, first that it often happens that three of the causes combine into one, such that the formal cause and the final cause are one in number.
     
     This must be understood to apply to the final cause of generation, not, however, to the final cause of the thing generated. For the end of the generation of man is the human form, but this form is not the end of man. Rather through this form man acts for his end.

The examples you give of cars and knives are strictly artifacts, not natural (or "birthed") things. Still, the final cause of making a car or knife is different from the final cause of the car or knife themselves.

Also, another term for a final cause is "the cause of causes" (causa causarum) because if it were not the first cause in the order of generation, the efficient cause would have no end toward which to act, and agents only act toward one end.

In ibid. l. 5, St. Thomas shows how the other three causes act because of or for the sake of the final cause:

186. …the final cause is the cause of the other causes. It is clear that the agent acts for the sake of the end. And likewise it was shown above[L4 #173] in regard to artificial things that the form is ordered to use as to an end, and matter is ordered to form as to an end. And to this extent the end is called the cause of causes.

Answer 2

Although Aristotle is not explicit about it, the answer seems to be yes. For example, Aristotle notes that the formal and final cause are often the same, and arguably multiple forms can serve as formal causes. Concerning uniqueness of the formal cause here is a relevant passage from Kenny's Aquinas on Mind (p.149):

"Whenever there is a true sentence on the pattern ‘A is F’, we can speak of the form of F-ness; an accidental form or a substantial form as the case may be. If A is hot, there is such a thing as the hotness of A; if A is an animal, there is such a thing as the animality of A. Thus, the hotness, or heat, of a hot body is what makes it hot, and that is an example of an accidental form. The substantial form in a human being may likewise be introduced as being, truistically, that by which a man is a man, or that which makes a man a man. In each of these cases the ‘makes’ is the ‘makes’ of formal causality, as when we say that it is a certain shape which makes a piece of metal a key..."

In other words, a form does not have to be substantial to serve as a formal cause, and accidental forms are certainly not unique for a thing. Even if we assume that only substantial forms can serve as formal/final causes it is not clear that Aristotle asserts unicity even of substantial forms. Apparently, there was a controversy about it in Aquinas's time, which suggests to me that Aristotle was none too clear on the issue:

"Now human beings grow and take nourishment, just as vegetables do; they see and taste and run and sleep just as animals do. Does this mean that they have a vegetable and animal soul as well as a human soul? Many of Aquinas’ contemporaries answered this question in the affirmative. They held that in the human being there was not just a single form, the intellectual soul, but also animal and vegetable souls; and for good measure some of them added a further form, a form which made a human being a bodily being. This was a ‘form of corporeality’... Aquinas rejected this proliferation of substantial forms."

The "form of corporeality" comes from another well-known interpreter of Aristotle, Avicenna, see Pasnau's Form and Matter. But even if we accept Aquinas's position on unicity of the substantial form, assume (even against him) that only such a form can be a formal/final cause, and postulate some sort of analogous "ultimate" final cause in all cases, the final cause of final causes as it were, (which seems to be the idea in the OP), I do not see why Aristotle would want to restrict final causality to such a uber-cause. His four causes are devices of explanation, whenever a teleological explanation is called for in a particular context the thing will have a (context-dependent) final cause.

Think of an architect building a castle, his various construction decisions aiming at making it defensible, imposing, pleasing to the eye, etc., all of this together wraps into a final cause he is working towards. But then think of the architect's client, the king, who sees it as a strategic piece in a grand plan for expanding the kingdom, and cares little for, or does not even know, the construction details, while the architect has not a clue about the grand plan. Which is the castle's final cause? The architect's and the king's designs overlap, but none contains the other, and while we could wrap them together artificially, the explanatory value of such a chimera is dubious. There might also be a problem with this "ultimate" cause itself because Aristotle rejects actual infinity. It is one thing to potentially have a final cause in any context, it is quite another to actualize them all into an "ultimate" cause.

Answer 3

Aristotle does comment, as a matter of fact, on the uniqueness of final causes. He does it near the beginning of the Politics, where he discusses the "natural roles" of men, women, children, slaves, Greeks and barbarians. He states there that an artifact sometimes has more than one final cause (= inherent purpose), while a being produced by nature always has a single final cause. Nature assigns a single final cause, because this is best. And nature does what is best, and also does not spare any expenses.

For he who can foresee with his mind is by nature intended to be lord and master, and he who can work with his body is a subject, and by nature a slave; hence master and slave have the same interest. Nature, however, has distinguished between the female and the slave. For she [=nature] is not niggardly, like the smith who fashions the Delphian knife for many uses; she [=nature] makes each thing for a single use, and every instrument is best made when intended for one and not for many uses.

Answer 4

It seems you are using the singularity of the "output" (purpose) to imply (require) the singularity of the "input" (final cause).

It is certainly possible to have a single input (cause) for a given output (purpose), but it is also possible to have multiple inputs (contributing causes) for a single output (purpose).