The Design Argument: Evidence for God's Existence through Intelligent Design, Study Guides, Projects, Research of Design

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The design argument

The different versions of the cosmological argument we discussed over the last few weeks were arguments for the existence of God based on extremely abstract and general features of the universe, such as the fact that some things come into existence, and that there are some contingent things. The argument we’ll be discussing today is not like this. The basic idea of the argument is that if we pay close attention to the details of the universe in which we live, we’ll be able to see that that universe must have been created by an intelligent designer. This design argument , or, as its sometimes called, the teleological argument , has probably been the most influential argument for the existence of God throughout most of history. You will by now not be surprised that a version of the teleological argument can be found in the writings of Thomas Aquinas.

Later writers filled this gap in Aquinas’ argument, by providing reasons to think that the end-directed behavior of living things shows that the universe must have been designed. Perhaps the fullest development of this argument was provided by William Paley, an 18th century English philosopher and theologian, in his book Natural Theology. This book is filled with careful and detailed discussions of various facets of the natural world, each of which Paley employs in his argument for the existence of an intelligent designer of the universe. A representative, and historically important, example is Paley’s discussion of the eye. One might reasonably think that this needs a bit more argument: why, exactly, should we believe that the fact that plants typically act “to obtain the best result” shows that they are guided by something which has knowledge of their ends?

A representative, and historically important, example is Paley’s discussion of the eye. Here, as in many other places throughout the book, Paley is comparing an aspect of the natural world - in this case, the construction of the eye - and an artefact -- in this case, a telescope. The resemblance between the two is that both the parts of the eye and the parts of the telescope are set up perfectly for a certain purpose: in this case, the production of an accurate image of physical objects on the basis of the light reflected off of those objects. Further, Paley emphasizes, in either case very small changes to the parts of the instrument, or the way that they are combined, would make the instrument wholly unable to serve its purpose.

Would we, in this case, believe that the watch must have been designed by some intelligent watchmaker or other, or would we think that, for example, the watch simply came to be by chance? The answer, Paley thinks, is clear: we would conclude that it must have been designed by an intelligent watchmaker. The opposite view seems ridiculous. But, Paley thinks, this is exactly the view into which an atheist is forced. After all, we see in the world around us many examples of things, like the eyes of animals, which show the marks of design. This is relevantly just like finding a bunch of watches without knowing where they came from: we have found a whole world of well-designed creatures rather than just a single watch; so if it was reasonable to conclude that a watch must have been designed by an intelligent watchmaker, it is that much more reasonable to conclude that the natural world we find around us must have been designed by an intelligent creator.

But, Paley thinks, this is exactly the view into which an atheist is forced. After all, we see in the world around us many examples of things, like the eyes of animals, which show the marks of design. This is relevantly just like finding a bunch of watches without knowing where they came from: we have found a whole world of well-designed creatures rather than just a single watch; so if it was reasonable to conclude that a watch must have been designed by an intelligent watchmaker, it is that much more reasonable to conclude that the natural world we find around us must have been designed by an intelligent creator. Here is one way to make Paley’s line of reasoning explicit; as above, let’s say that an object has the “marks of design” if its parts are finely-tuned to its purpose.

1. Many things in nature, like eyes, show the marks of design.
2. These things must either have been created by an intelligent designer or produced by random natural processes.
3. Random natural processes never, or almost never, produce things with the marks of design.

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C. Things in nature that show the marks of design are very likely to have been created by an intelligent designer. (1,2,3) Paley’s design argument

Consider, for example, Darwin’s discussion of the eye:

1. Many things in nature, like eyes, show the marks of design.
2. These things must either have been created by an intelligent designer or produced by random natural processes. 3. Random natural processes never, or almost never, produce things with the marks of design.

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C. Things in nature that show the marks of design are very likely to have been created by an intelligent designer. (1,2,3) Paley’s design argument

Darwin’s theory shows how random natural processes could, over time, produce things with the marks of design. This theory seems to destroy Paley’s argument, as Darwin himself noted in his autobiography: Often very bold claims are made on behalf of the theory of evolution; sometimes it is even claimed that the theory shows that God does not exist. It is hard to see why this should be so. But it does seem that the theory undermines one historically important argument for the existence of God. The theory of evolution does not, however, destroy every version of the design argument, since not all versions of the design argument are based on the explanation of the features of living things.

1. Many things in nature, like eyes, show the marks of design.
2. These things must either have been created by an intelligent designer or produced by random natural processes. 3. Random natural processes never, or almost never, produce things with the marks of design.

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C. Things in nature that show the marks of design are very likely to have been created by an intelligent designer. (1,2,3) Paley’s design argument “The old argument of design in nature, as given by Paley, which formerly seemed to me so conclusive, fails, now that the law of natural selection had been discovered. We can no longer argue that, for instance, the beautiful hinge of a bivalve shell must have been made by an intelligent being, like the hinge of a door by man. There seems to be no more design in the variability of organic beings and in the action of natural selection, than in the course which the wind blows. Everything in nature is the result of fixed laws.” One might think of Darwin’s reply to Paley as posing a challenge to the defender of the design argument: which aspects the universe are not explained by the theory of evolution by natural selection, and yet are such that they are better explained by God than by chance?

These remarks can be turned into an argument for the existence of God. (Though, as we’ll see, it is not an argument that Rees himself accepts.) To see how this argument works, we will have to think a bit about what sorts of evidence can confirm a theory. Consider the following two theories: T1: It rained last night. T2: It did not rain last night. Suppose that I an considering these two theories this morning as I walk out of my front door, and, as I walk out the door, I come across a bit of evidence which might help me decide which of T1 and T2 are true: E: My sidewalk is wet. Does E count in favor of T1 or T2? Why? One natural answer is that E counts in favor of T1 because of the following fact: if T1 is true, then E is quite likely to be true, whereas if T2 is true, E is quite unlikely to be true. This suggests the following principle of confirmation : Evidence E favors T1 over T2 if E would be more likely to be true if T1 is true than if T2 is true.

One natural answer is that E counts in favor of T1 because of the following fact: if T1 is true, then E is quite likely to be true, whereas if T2 is true, E is quite unlikely to be true. This suggests the following principle of confirmation : Evidence E favors T1 over T2 if E would be more likely to be true if T1 is true than if T2 is true. Using the language of probability, this can be put as follows. To talk about the likelihood of an event happening is to talk about its probability , which can be represented as a number between 0 and 1. We can also talk about conditional probability , which is the likelihood of something to happen in the condition that something else happens. When we want to talk about the likelihood of X happening if Y happens, we talk about the probability of X given Y. In these terms, we can state the principle of confirmation as follows: The principle of confirmation E is evidence for T1 over T2 if the probability of E given T1 > the probability of E given T2.

Now consider the following piece of evidence which we seem to possess: LIFE: The universe is such as to permit life to exist. And now consider the following two theories about the universe: CREATION: The universe was designed by a creator who wanted life to exist. CHANCE: The basic physical constants of the universe are due to chance, rather than intelligent design. If this is correct, then it follows from what we have said so far that LIFE is extremely strong evidence that CREATION, rather than CHANCE, is the correct theory. The principle of confirmation E is evidence for T1 over T2 if the probability of E given T1 > the probability of E given T2. This is often called the fine-tuning argument for God’s existence. It may be put as follows: The fine-tuning argument

1. The probability of LIFE given CREATION is extremely high.
2. The probability of LIFE given CHANCE is extremely low.
3. The principle of confirmation. C. LIFE is evidence for CREATION over CHANCE.

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The principle of confirmation E is evidence for T1 over T2 if the probability of E given T1 > the probability of E given T2. Above I mentioned that Rees does himself find this use of his ideas convincing; let’s see why by expanding the quotation discussed above. The fine-tuning argument

1. The probability of LIFE given CREATION is extremely high.
2. The probability of LIFE given CHANCE is extremely low.
3. The principle of confirmation. C. LIFE is evidence for CREATION over CHANCE.

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The principle of confirmation E is evidence for T1 over T2 if the probability of E given T1 > the probability of E given T2. So if we have good reason to believe in the multiverse, this has the makings of a good objection to the fine- tuning argument. But do we have good reason to believe in the multiverse? One might think that LIFE provides us with extremely strong evidence for the existence of the multiverse. After all, isn’t the probability that a universe is life-permitting given the existence of the multiverse higher than if not? If so, the principle of confirmation itself seems to count strongly in favor of the multiverse. But this is argument is not convincing. Consider the following analogy: I am sitting in my office, and I pick up 12 dice and decide to roll them. I roll all sixes. Amazed, I think to myself: there must be lots of people rolling dice in Malloy Hall right now. After all, what are the odds that someone rolls 12 sixes in Malloy in the case where there is just one person rolling dice? Something is odd here; my rolling 12 sixes is certainly surprising, but it is not evidence for the existence of many rollers. Why not? The explanation of what’s going on here shows that we have to be careful in thinking about what, exactly, our evidence is. In particular, we need to keep the following two pieces of evidence separate: Evidence 1: I rolled 12 sixes. Evidence 2: Someone in Malloy Hall rolled 12 sixes. The fine-tuning argument

1. The probability of LIFE given CREATION is extremely high.
2. The probability of LIFE given CHANCE is extremely low.
3. The principle of confirmation. C. LIFE is evidence for CREATION over CHANCE.

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The principle of confirmation E is evidence for T1 over T2 if the probability of E given T1 > the probability of E given T2. One might think that LIFE provides us with extremely strong evidence for the existence of the multiverse. After all, isn’t the probability that a universe is life-permitting given the existence of the multiverse higher than if not? If so, the principle of confirmation itself seems to count strongly in favor of the multiverse. I am sitting in my office, and I pick up 12 dice and decide to roll them. I roll all sixes. Amazed, I think to myself: there must be lots of people rolling dice in Malloy Hall right now. After all, what are the odds that someone rolls 12 sixes in Malloy in the case where there is just one person rolling dice? The explanation of what’s going on here shows that we have to be careful in thinking about what, exactly, our evidence is. In particular, we need to keep the following two pieces of evidence separate: Evidence 1: I rolled 12 sixes. Evidence 2: Someone in Malloy Hall rolled 12 sixes. If my evidence is #2, then it looks like I have some evidence for the existence of many rollers. But in the above case my evidence is #1; and the existence of many rollers would not make it more likely that I would roll 12 sixes. Now think about the fine-tuning argument and the multiverse. Just as in the dice case, we have to be careful to distinguish the following two pieces of evidence: Evidence 1: This particular universe is life supporting. Evidence 2: Some universe or other is life-supporting. Which piece of evidence do we have? What does this show about the argument that LIFE is evidence for the existence of the multiverse? The fine-tuning argument

1. The probability of LIFE given CREATION is extremely high.
2. The probability of LIFE given CHANCE is extremely low.
3. The principle of confirmation. C. LIFE is evidence for CREATION over CHANCE.

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