Consider this the first part of a long post on Aquinas’ arguments for the unity of man’s ultimate end. The second part will evaluate Aquinas’s arguments and defend them from several objections.

As we pointed out in an earlier post, Aquinas makes three claims about the final end of the human person in question 1 of the Treatise on Happiness:

1. Every person has a final end that gives intentional or practical unity to their lives (q. 1, a. 3-4).
2. Every person has exactly one final end (q. 1, a. 5).
3. Every individual person has the same final end as every other individual person (q. 1, a. 7)

I’ll admit that Aquinas’s argument for (2) has given me some trouble in the past, so we’ll analyze it here today.

Aquinas’s Argument for the Unity of the Ultimate End

In q.1 a. 4, Aquinas argues that whenever we consider some bit of practical reasoning–say, changing a flat car tire in order to get the car moving again, in order to reach the dance recital on time–there are two “orders,” or rational principles, governing the chain of reasoning. On the one hand, if someone asks why we are changing the car tire, he’s asking about the order of intention: what goal are we aiming at by changing the car tire? (Many answers are possible: building a realistic car sculpture; practicing for pit crew for the Indy 500, etc.). On the other hand, if someone knows both that we’re headed to the dance recital and that we have a flat tire, he might ask: how are you going to get to the recital on time? Here he’s asking about the order of execution, that is, the means by which we’re going to achieve our goals.

Both the order of intention and the order of execution can consist of an indefinite number of actions. Just changing a car tire involves a plurality of steps: you have to locate the lugnuts, lugwrench and carjack, jack the car, remove the nuts and the tire, etc.; and once that task is complete, there are the countless little actions one must take while driving (e.g., operating the pedals, judging the fastest route) in order to make it to the dance recital on time. The same is true for the order of intention, which involves many of the same actions, understood now as ends: we locate the lugnuts for the sake of removing the tire, which we remove for the sake of replacing the tire, which we replace for the sake of returning the car to the road, etc.

This much is straightforward. Now comes the key move. Aquinas argues that, in any actual and unified action, there must be something first in both the order of intention and in the order or execution (q. 1, a. 4). In other words, every actual and unified action must have a definite beginning (of execution) and end (of intention); an infinite series is impossible in either direction. Here’s how Aquinas puts it:

there is to be observed a twofold order in ends—the order of intention and the order of execution: and in either of these orders there must be something first. For that which is first in the order of intention, is the principle, as it were, moving the appetite; consequently, if you remove this principle, there will be nothing to move the appetite. On the other hand, the principle in execution is that wherein operation has its beginning; and if this principle be taken away, no one will begin to work. Now the principle in the intention is the last end; while the principle in execution is the first of the things which are ordained to the end. Consequently, on neither side is it possible to go to infinity since if there were no last end, nothing would be desired, nor would any action have its term, nor would the intention of the agent be at rest; while if there is no first thing among those that are ordained to the end, none would begin to work at anything, and counsel would have no term, but would continue indefinitely.

Consider, first, that we’re changing the car tire in order to get to the dance recital. Aquinas’ argument presupposes that we can identify a specific series of changes in the world as falling under this description, and that this description excludes other changes occurring in the world at the same time (the price of rice in China; Mr. T’s new favorite color). This is what we mean by saying that Aquinas’s analysis is limited to a unified series of actions: that the individual actions within the series are related to one another as means to ends, not by chance, but according to some rational principle that gives intelligibility or meaning to the series.

Now if there were nothing first in the order of execution, there would be literally no beginning to “changing the car tire.” Should that happen, Aquinas dryly observes, “no one will begin to work.” We have all observed the truth of this statement. Telling a group of young cub scouts to change a tire is nearly as useless as asking a group of college freshman  to engage in philosophical thinking: both will stare blankly at you because they don’t know how to begin. On the other hand, if there were nothing first in the order of intention, that is, no last thing that one is aiming at, “there will be nothing moving the appetite”: one will have no action at all to think about. For the end or goal or intention at which one aims is what gives meaning and value to the series of actions in the first place: that I need to get to the dance recital is what motivates me to change the car tire rather than taking out my iPad to play games, and is also what makes changing the tire but not playing the iPad a means to that goal. So long as we are speaking of one action (changing the care tire to get to the recital), then, that action must have a definite beginning and a definite end; lacking either, we would simply have no action at all. (By supposition, we do have an action–changing the car tire–so by reductio ad absurdam, the action must have a beginning and an end.)

It follows, Aquinas thinks, that insofar as the final end in the order of intention actually orders one’s actions in one way rather than another, one action cannot simultaneously have more than one final end. An action (even when that ‘action’ involves many steps in the order of execution) is one by virtue of having one final end. One action cannot simultaneously have more than one ultimate end, because that would be the impossible equivalent of driving with two simultaneous destinations: you cannot, at one and the same time, be on your way to both Boston and Los Angeles.

Now, as we have argued earlier, Aquinas thinks that what is true of action is true of the life of persons. That’s the point of talking about Aquinas’s narrative conception of the person, namely, that there is a practical unity in one’s life that orders and gives value to one’s life just as there is a practical unity in an action (like changing a car tire) that orders and gives value to that action. Just as there is a single, unified end to changing a car tire–making it to the dance recital, in this case–so too, Aquinas argues, is there a single, unified end to one’s life. This is, as I understand it, the third argument Aquinas gives for (2) in q. 1, a. 5c:

since voluntary actions receive their species from the end, as stated above, they must needs receive their genus from the last end, which is common to them all: just as natural things are placed in a genus according to a common form. Since, then, all things that can be desired by the will, belong, as such, to one genus, the last end must needs be one. And all the more because in every genus there is one first principle; and the last end has the nature of a first principle, as stated above.

Coming Soon: Aquinas on the Unity of Our Final End, Part 2: Against Serial Teleologists!