The Design Argument
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Chapter5TheDesignArgument.docxChapter 5 The Design Argument
Chapter Outline
2. Two Kinds of Design Argument
4. The Analogy
5. Abductive Arguments Often Postulate Unobserved Entities
6. Hume’s Criticisms of the Design Argument
7. Is the Design Argument a Weak Argument from Analogy?
8. Is the Design Argument a Weak Induction?
There are three main traditional arguments for the existence of God—the cosmological argument, the design argument, and the ontological argument. Aquinas’s first, second, and third ways, surveyed in the previous chapter, are cosmological arguments. Cosmological arguments take different forms; each cites a general feature of the whole universe as evidence that there is a God. The second type of traditional argument, the design argument, is the one we’ll consider in the present chapter. The ontological argument will occupy our attention in Chapter 8 .
Aquinas’s fifth argument for the existence of God is an instance of what has come to be called the Argument from Design. The design argument has a variety of forms, some of which I’ll describe. To start things off, here is a formulation that is close to the one Aquinas uses:
1. Among objects that act for an end, some have minds whereas others do not.
2. An object that acts for an end, but does not itself have a mind, must have been designed by a being that has a mind.
3. Hence, there exists a being with a mind who designed all mindless objects that act for an end. Hence, God exists.
Note as a preliminary point that the transition from (2) to (3) commits the Birthday Fallacy described in Chapter 4 . If each mindless object that acts for an end has a designer, it doesn’t follow that there is a single designer of all the mindless objects that act for an end.
Goal-Directed Systems
What does Aquinas mean by “act for an end”? This phrase corresponds to the modern idea of a goal-directed system. Human beings act for an end because they have desires; these desires represent the ends or purposes or goals to which behaviors are directed. Human beings are capable of goal-directed behavior because they have minds. Consider, however, a different example: a guided missile. It is a goal-directed system. Its goal or function is to reach and destroy its target. If the target veers off to the side, the missile can adjust its behavior so that it will achieve its purpose. Guided missiles are goal-directed systems, but they don’t have minds. How is this possible? The answer is consistent with what Aquinas says in premise (2). Guided missiles are artifacts. They are devices built by creatures with minds—namely, human beings. This is how missiles obtained the machinery that allows them to engage in goal-directed behavior.
Are there other examples of goal-directed systems besides human beings and artifacts? Nonhuman organisms provide a third category. Even bacteria, which evidently don’t have beliefs and desires, seek out nutrients and avoid poisonous chemicals. Because of this, it seems plausible to describe them as having the goal of surviving and reproducing. They are able to modify their behavior to achieve these ends.
Does the list stop with human beings, artifacts, and nonhuman organisms? Aquinas followed Aristotle in thinking that even inanimate objects such as rocks and comets have goals. This idea went out of fashion with the Scientific Revolution in the seventeenth century. It now seems implausible to describe a rock as being hard “in order to resist destruction.” It also seems strange to say that rocks fall toward the center of the Earth when they are released “in order to attain the location that it is in their nature to seek.” But this is how Aristotle thought about rocks, and Aquinas followed him here. Both thought that everything, whether living or not, should be understood teleologically—that is, as a goal-directed system. (This will be discussed further in Chapter 34 .) I won’t take issue with this general teleological picture, except to note that it is far more encompassing than the one provided by modern science. However, this point does not affect the design argument as I have formulated it. What is required is just that some mindless objects are goal directed.
Two Kinds of Design Argument
It will be useful to distinguish two kinds of design argument. Aquinas would have been willing to endorse them both. David Hume (1711–1776), who examined various design arguments in his Dialogues Concerning Natural Religion (1779), discusses both sorts. I’ll call these two sorts of arguments global and local design arguments.
A global design argument cites some general features of the whole universe and argues that this feature should be explained by the hypothesis that it is the product of intelligent design. An example would be the argument that proposes to explain why the laws of nature are simple. Newton himself argued that the simplicity of natural laws is evidence that there exists an intelligent and perfect God who was their author.
A local design argument focuses on a more specific feature that one or more object in the universe has and claims that the hypothesis that God exists is the best or the only plausible explanation of that fact. The example I’ll consider here concerns features of the organisms we observe on Earth. They are goal-directed systems; they are complex systems equipped with the ability to modify their behavior so that they can survive and reproduce. In this chapter, I’ll focus on the local argument, which claims that special features of living things (including ourselves) are said to require explanation. In Chapter 7 , I’ll return to design arguments that are global.
The Analogy
So far in this argument, Paley is simply describing what common sense would say about the watch on the beach. Paley then suggests an analogy. Look around the living world. Notice that it is filled with organisms that are extremely intricate and well adapted to living in the environments they inhabit. In fact, organisms are far more complicated than watches. And as well suited as a watch is to the task of measuring time, organisms are even better suited to the tasks of surviving and reproducing.
How can we explain the fact that organisms are so amazingly intricate and well adapted? One possibility is the Random Hypothesis—that by a process akin to waves pounding on sand, orchids, crocodiles, and people came into existence. The other alternative is the Design Hypothesis—that an organism maker made the impressive pieces of machinery we call living things. Which explanation is more plausible? If the Random Hypothesis says that the existence of the watch is very improbable, then the Random Hypothesis must also say that the existence of these intricate and adapted organisms is very improbable. So if inferring the existence of a watchmaker is plausible in the first case, then inferring the existence of a designer of all life is plausible in the second.
Finally, we may ask how intelligent this maker of organisms must be, given the intricacy and fineness of adaptation that organisms exhibit. From what watches are like, we can infer that watchmakers must be pretty smart. By the same reasoning, we infer that the maker of organisms must be very, very intelligent—far more intelligent than human beings are. Paley’s design argument concludes that the intricacy and adaptedness of organisms are best explained by postulating the existence of an extremely intelligent designer.
Abductive Arguments Often Postulate Unobserved Entities
There is a point that pertains to all of Aquinas’s arguments that should be emphasized here. The design argument claims that there is something we observe—the complexity and adaptedness of living things—that is best explained by the hypothesis that there is a God. The conclusion of the argument concerns the existence of something we have not directly observed. Although there may be defects in this argument, the fact that it reaches a conclusion about a being we have not observed isn’t one of them. Recall from Chapter 3 that abductive arguments frequently have this characteristic. It would cripple science to limit theorizing to a description of what scientists have actually observed. So my view of Paley’s argument is that it is an abductive argument:
· Organisms are intricate and well suited to the tasks of survival and reproduction.
·
· Hence, organisms were created by an intelligent designer.
I’ve drawn a double line here to indicate that the argument does not aim at being deductively valid.
To show this is a strong abductive argument, Paley argues that it is analogous to a second inference to the best explanation:
· The watch is intricate and well suited to the task of measuring time.
·
· Hence, the watch was created by an intelligent designer.
Paley claims that if you grant that the watch argument is convincing, you should grant that the organism argument is convincing as well.
Is the Design Argument a Weak Argument from Analogy?
In this section, I’ll discuss a criticism of the argument from design that Hume develops in Part II of his Dialogues (see the paragraph beginning “What I chiefly scruple …”).
To see what Hume has in mind when he talks about arguments from analogy, consider the following example of an analogy argument:
· Human beings circulate their blood.
·
· Dogs circulate their blood.
I’ve drawn a double line between the premise and the conclusion, again to indicate that the argument isn’t supposed to be deductively valid. In this argument, let’s call human beings the analogs and dogs the targets. I say that dogs are the targets here because they are the items about which the argument aims to reach a conclusion. Hume suggests, with some plausibility, that such arguments are stronger or weaker depending on how similar the analogs are to the targets. To see what he means here, compare the above argument with the following one:
· Human beings circulate their blood.
·
· Plants circulate their blood.
This argument is pretty weak because human beings and plants aren’t very similar.
We can formulate Hume’s point by saying that an analogy argument has the following logical form:
· Object A has property P.
· Object A and object T are similar to degree n.
· n[
· T has property P.
A is the analog and T is the target. The number n measures the degree of similarity between A and T. It goes from a minimum value of 0 (meaning that A and Taren’t similar at all) to a maximum value of 1 (meaning that they share 100 percent of their characteristics). This number also represents a probability—that is why “n” is next to the double line separating premises from conclusion. A high value of n means that A and T are very similar and that the premises make the conclusion very probable. This expresses Hume’s idea that the more similar A and T are, the more probable it is that the target object T has the property that is found in the analog A.
Hume uses this idea about analogy arguments to criticize the design argument. He thinks the design argument has the following form:
· Watches are products of intelligent design.
· n[
· The universe is a product of intelligent design.
This is a very weak argument, Hume says, as the analog is really not very similar to the target. Watches resemble the universe as a whole in some ways, but fail to do so in a great many others. So n has a low value.
Here Hume is criticizing what I’ve called a global design argument—an argument that focuses on some large-scale features of the entire universe. Hume’s point, however, also applies to local design arguments—to arguments that focus on organisms and their characteristics:
· Watches are products of intelligent design.
· n[
· Organisms are products of intelligent design.
Hume’s criticism is that organisms are really not very similar to watches. Watches are made of metal, but organisms aren’t. Kangaroos hop around, but watches don’t. Organisms reproduce and obtain nutrition from their environment, but watches don’t. And so on. As analog and target are so dissimilar, the analogy argument is a very weak one; n is low here as well.
Hume’s idea is that the strength or weakness of an analogy argument depends on the overall similarity of target and analog. You look at all the known characteristics of target and analog and try to say how similar they are overall. I grant that if you did this, you would conclude that watches and kangaroos aren’t very similar. My view, however, is that this doesn’t undermine the design argument at all when that argument is taken to be abductive. It is entirely irrelevant whether watches and kangaroos both have fur, or whether both hop around, or whether both reproduce. The design argument focuses on a single pair of featuresof each of these and asks how it should be explained. A watch’s intricacy, as well as its being well suited to the task of measuring time, requires that we think of it as the product of intelligent design. Paley’s claim is that an organism’s intricacy, as well as its being well suited to the tasks of survival and reproduction, ought to be explained in the same way. It doesn’t matter that the one is made of metal while the other isn’t. Overall similarity is irrelevant.
The fundamental idea of Paley’s argument is that the Surprise Principle tells us that the Design Hypothesis is better supported than the Random Hypothesis, given the observations we have made about living things. This argument stands on its own. To use the Surprise Principle in this case, it doesn’t matter whether organisms are similar to watches or to anything else. I conclude that Hume is mistaken to criticize the design argument as a weak argument from analogy.
Is the Design Argument a Weak Induction?
A second criticism that Hume levels at the design argument rests on his assuming that the argument must be inductive if it is to make sense. (Here I have in mind the paragraph in Part II of the Dialogues that begins “And can you blame me …’’; see especially the passage that begins “When two species of objects …”)
Recall from Chapter 2 that inductive arguments involve observing a sample and extrapolating from it to some claim about one or more objects not in the sample. For example, suppose I call a large number of voters registered in a county and find that most of them are Democrats. This seems to license the inference that the next voter I call will probably be a Democrat. Hume observes, again with some plausibility, that the strength of an inductive inference is influenced by sample size. In particular, if my sample had included only five individuals, I would be on rather shaky ground if I used this as my basis for predicting what the next voter called would be like. My inference would be on even shakier ground if I ventured a guess about the next telephone call having never sampled even a single voter. A sample size of zero is just plain silly; an inductive argument can’t be weaker than that.
Hume claims that if we are to have a reason for thinking that the universe we inhabit is the product of intelligent design, we must base this conclusion on induction. What would this involve? We would have to examine a large number of other universes and see that most or all of them were the result of intelligent design. If our sample size were sufficiently large, that would justify a conclusion about the universe that we inhabit. But how big is our sample size? How many universes have we observed being made by an intelligent designer? The answer is zero. The only universe we have ever experienced is the one we inhabit. We have not seen our universe being made by an intelligent designer, nor have we seen an intelligent designer make the organisms that exist in our universe. So no inductive argument can be constructed here.
My view is that this is true, but irrelevant. Small sample size does weaken an inductive argument. However, the design argument isn’t an inductive argument. Hume assumed that the only sorts of inferences worth taking seriously are inductive and deductive. I think this is a mistake. There is abduction as well. Mendel didn’t have to observe that lots of different organisms have genes before he could conclude that his pea plants have genes. Mendel never saw a single gene, but that didn’t prevent him from inferring their existence. His inference was abductive, not inductive.
I’ve reviewed two of Hume’s criticisms of the design argument. They don’t work. Of course, this doesn’t mean that the argument has no flaws, only that we have yet to uncover one. The design argument that Paley formulated considers two competing hypotheses—the hypothesis of intelligent design and the hypothesis of random physical processes. In the mid-nineteenth century, a new hypothesis was formulated that we now need to consider as a third alternative—this is Darwin’s theory of evolution by natural selection. In the next chapter, I’ll describe what this hypothesis asserts and discuss how it compares with the hypothesis of intelligent design.
Review Questions
1. What does it mean to say that the design argument is an abductive argument?
2. What is the difference between a global design argument and a local design argument?
3. How does Paley’s argument about the watch use the Surprise Principle?
4. Hume formulated a principle that states how the strength of an analogy argument may be measured. What is it?
5. What two criticisms did Hume make of the design argument? Are these good criticisms if the argument is understood to be abductive in character?
Problems for Further Thought
1. It might be suggested that one difference between Paley’s argument about the watch and his argument about organisms is that we have seen watchmakers, but have never directly observed God. Does this point of difference undermine the force of Paley’s design argument?
2. I mentioned in passing that modern science no longer takes seriously the idea that all things are goal-directed systems. Consider the following pair of propositions. Can you think of a reason that the first of them might be true, whereas the second might be rejected?
· The function of the heart is to pump blood.
· The function of rain is to provide farm crops with water.
· What does it mean to attribute a “function” to something?
3. In addition to the two criticisms that Hume makes of the design argument that are described in this chapter, Hume presents a third. He says that even if the design argument succeeds in showing that a designer made the universe (or the organisms in it), it does not succeed in establishing what characteristics that designer has. For this reason, the argument does not show that God exists. Is Hume’s claim correct? How seriously does this undermine the design argument?
