Weakness of Analogy
One objection to the argument just set forth is that it relies on a weak analogy: it takes for granted that there is a significant resemblance between natural objects and objects which we know to have been designed. But it is not obvious that, to use the same example again, the human eye really is like a watch in any important respect. Arguments from analogy rely on there being a strong similarity between the two things being compared. If the similarity is weak, then the conclusions that can be drawn on the basis of the comparison are correspondingly weak. So, for example, a wrist watch and a pocket watch are sufficiently similar for us to be able to assume that they were both designed by watchmakers. But although there is some similarity between a watch and an eye – they are both intricate and fulfil their particular functions – it is only a vague similarity, and any conclusions based on the analogy will as a result be correspondingly vague.
Against this criticism a Theist might still maintain that it is more likely that the eye was designed by a supreme being than that it came about merely by chance.
The existence of a Divine Watchmaker is not, however, the only possible explanation of how it is that animals and plants are so well adapted to their functions. In particular, Charles Darwin’s (1809–82)
theory of evolution by natural selection, explained in his book The Origin of Species
(1859), gives a widely accepted alternative explanation of this phenomenon. Darwin showed how, by a process of the survival of the fittest, those animals and plants best suited to their environments lived to pass on their characteristics to their offspring. Later scientists have been able to account for the mechanism of evolution in terms of inherited genes. This process explains how such marvellous adaptations to environment as are found in the animal and plant kingdoms could have occurred, without needing to introduce the notion of God.
Of course Darwin’s theory of evolution in no way disproves God’s existence – indeed, many Christians accept it as the best explanation of how plants, animals, and human beings came to be as they are: they believe that God created the mechanism of evolution itself. However, Darwin’s theory does weaken the power of the Design Argument since it explains the same effects without any mention of God as their cause. The existence of such a theory about the mechanism of biological adaptation prevents the Design Argument from being a conclusive proof of God’s existence.
Limitations on Conclusion
Even if, despite the objections mentioned so far, you still find the Design Argument convincing, you should notice that it doesn’t prove the existence of a unique, all-powerful, all-knowing, and all-good God. Close examination of the argument shows it to be limited in a number of ways.
First, the argument completely fails to support monotheism – the view that there is just one God. Even if you accept that the world and everything in it clearly shows evidence of having been designed, there is no reason to believe that it was all designed by one God. Why couldn’t it have been designed by a team of lesser gods working together? After all, most large-scale, complex human constructions such as skyscrapers, pyramids, space rockets, and so on, were made by teams of individuals, so surely if we carry the analogy to its logical conclusion it will lead us to believe that the world was designed by a group of gods working together.
Second, the argument doesn’t necessarily support the view that the Designer (or designers) was all-powerful. It could plausibly be
argued that the universe has a number of ‘design faults’: for instance, the human eye has a tendency to short-sightedness, and to cataracts in old age – hardly the work of an all-powerful Creator wanting to create the best world possible. Such observations might lead some people to think that the Designer of the universe, far from being all-powerful, was a comparatively weak god or gods, or possibly a young god experimenting with his or her powers. Maybe the Designer died soon after creating the universe, allowing it to run down of its own accord. The Design Argument provides at least as much evidence for these conclusions as it does for the existence of the God described by the Theists. So the Design Argument alone cannot prove that the Theists’ God rather than some other type of God or gods exists.
Finally, on the question of whether the Designer is all-knowing and all-good, many people find the amount of evil in the world counts against this conclusion. This evil ranges from human cruelty, murder, and torture, to the suffering caused by natural disasters and disease. If, as the Design Argument suggests, we are to look around us to see the evidence of God’s work, many people will find it hard to accept that what they see is the result of a benevolent Creator. An all-knowing God would know that evil exists; an all-powerful God would be able to prevent it occurring; and an all-good God would not want it to exist. But evil continues to occur. This serious challenge to belief in the Theists’ God has been much discussed by philosophers. It is known as the Problem of Evil. In a later section we will examine it in some detail, together with several attempted solutions to it. Here it should at least make us wary about claims that the Design Argument provides conclusive evidence for the existence of a supremely good God.
As can be seen from this discussion, the Design Argument can only give us, at best, the very limited conclusion that the world and everything in it was designed by something or someone. To go beyond this would be to overstep what can logically be concluded from the argument.