1. Watches require a designer.
2. The universe is like a watch.
3. Therefore the universe requires a designer.
The first premise we take to be obvious. The second premise is supported by the complexity and functions of organisms. The parts of an organism function to maintain the existence of the organism of which they are part. Paley's favorite example is the eye which has a large number of parts that interact in a complex way in order to allow the organism to acquire information about its environment which it acts on in order to increase its chances of survival. The conclusion follows inductively, and its strength depends on the similarity of the two things and the lack of relevant differences between the two. The main relevant difference between organisms and watches is, of course, that organisms can evolve whereas watches cannot. So how does Ross defend Paley's analogy?
Ross considers three responses, from David Hume, Charles Darwin and Stephen Jay Gould, to Paley's analogy.
Hume: Ross mentions that Hume does not think the analogy is strong, and Ross then mentions Hume's alternative account of the appearance of design: "random shuffling of matter" (p. 100) in an infinitely old universe. Ross then ridicules Hume's alternative without even addressing the many differences Hume pointed out between human artifacts and organisms.
Clearly Hume did not know that the universe was finite in time, and he did not have Darwin's theory of natural selection. But Ross commits a false dilemma fallacy here. One cannot defend a divine origin as an explanation of function and complexity in organisms by rejecting an alternative. Hume's is not the only possible alternative. Rather Ross needs to address the reasons Hume gives for the differences between the two. Ross does not even mention these objections, and it would take too long to review them here. However, one point is that we must derive a conclusion about the whole universe based on the function of a small part. Another point is that we have never seen a universe made, nor seen anything made from similar materials. These differences weaken the argument, and Ross needs a response to them, but he does not even bother.
Another point Hume makes is that if we really take the analogy seriously we should not conclude that the universe had a single, perfect designer. We should not derive a conclusion that exceeds what is necessary to explain the effect, and since the universe is not perfect, there is no reason to conclude that the designer is perfect. Given the way the universe functions it could have been designed by, for example, an immature, unwise god, or a senile, demented god. Similarly, when we look at human artifacts, we never find a single designer who controls all aspects of creation from concept to completion. Instead we find groups of people who work on pre-existing designs, making small improvements over them, and working together to construct artifacts according to those designs. Thus, if we take the design argument seriously, we would be better justified in concluding that there are many, imperfect designers working together to create the universe. Strangely, people rarely draw this conclusion.
Darwin: Ross briefly describes Darwin's view that natural selection can account for these features of organisms. Ross's rejection of Darwin is based on irrelevancies and incomplete consideration of the evidence. He claims that Darwin did not explain the origin of the first living organisms that were capable of evolving, that there is no evidence for large-scale evolutionary change, that it is impossible for species to evolve beyond a "species' norm" (p. 102), and that it is impossible for new species to appear as quickly as species become extinct. Finally, he claims that life is at all times becoming progressively less complex.
Obviously this is absurd. Ross's objection that Darwin does not explain the origin of the first living organisms is irrelevant to claims about Darwinian evolution. His rejection of evidence for large-scale evolutionary change (speciation) is simple denial of mountains of evidence. The impossibility of speciation is based only on our intuitions about breeding dogs to anything smaller than a dog. This totally misunderstands how speciation occurs; no one thinks that different species interbreed in order to produce a new species of offspring. Groups are thought to interbreed and change together to adapt to a changing environment. Finally, the evidence about extinction rates, based on current rates precipitated in part by human effects on animal habitats, are clearly irrelevant to overall extinction rates. And, in any case, he provides no reason at all to think that speciation could not occur as quickly as these long term extinction rates.
His alternative explanation, his way of trying to force the data to fit his own theory, is entertaining as well. He thinks that this purported excess of extinction supports the idea that God created all the existing species at once and time is slowly paring that number down. Why God would do such a crappy job of creating species that they would inevitably die out is never explained. Should we take Ross's theory seriously? Probably not, but let's do it anyway. If we take his low-end estimate of extinctions of one species per year, and the estimate that there are about 1.5 million species of organism currently on earth, we can conclude, given the fact that life has existed on earth for at least 3.5 billion years, that God must have created 3.5 billion species. (We can basically ignore the 1.5 million that currently exist as a roundoff error. My assumption is based on the assumption that the rate is constant, but it would probably be higher when there were more species to go extinct.) Since the earth is 197million square miles in area, we find that now each species has 131 square miles. But when God created all these species, they would have had only .056 square miles each. That's about 35 acres on average for each species. This isn't physically impossible, but it would be a tight fit.
Gould: Ross understands Gould as emphasizing bad designs in nature as evidence for natural selection rather than divine origin. Ross follows Gould's example of the panda's thumb as an limb jury-rigged from existing parts rather than something created from scratch. He gives three responses.
First, organisms are too complex for humans to draw conclusions about "the quality of the Creator's work." Aside from the obvious question-begging nature of this objection, this response is absurd. We can identify when something effectively fulfills a function. Is he seriously saying we cannot judge whether the panda's thumb is more or less effective than a human thumb?
Second, he claims that organisms might degrade over time from God's perfect design. Presumably they had a much more effective thumb and they only devolved to be less effective at eating bamboo. I would make fun of Ross for this, but I think his brain must have devolved from a state of perfection in order for him to think this, and I don't think it's nice to make fun of the devolved. Why would he think that pandas with less effective thumbs would be more likely to survive and reproduce than those whose thumbs were more effective? Perhaps he thinks that the thumb degenerated from a superior thumb by means of random mutation, but that would not explain at all why it would degenerate in a way that fit exactly with the "design" of other bears. Why, for example, would they have five fingers and a thumb rather than four fingers and a thumb as humans have? The only reasonable explanation is that the wrist bone mutated from a shorter wrist bone from related bears.
His third response is that Gould has no new explanation for this imperfect design, only "the already discredited Darwinist explanations" (p. 104). I can only laugh at this response.
Finally, his claim that organisms have become progressively less complex over time flies directly in the face of the evidence. Just to take one example, algae long preceding humans.
In sum, we can say that Ross does not exactly think through his advocacy of the argument from design. He does not make any serious attempt to describe, much less respond to, any real objection to Paley's design argument.