See here for content about the status as a proof and value for religious faith of arguments for the existence of God. It is also needed for some philosophy dialogues questions about the relevance of reason and philosophical argument for religious faith.
William Paley’s design qua Purpose is the argument that the combination of complexity and purpose are best explained by a designer.
Paley illustrates this with the example of a watch. If you were walking on a heath and came across a watch, you couldn’t argue it had come about by chance nor been there forever because it has Complexity & Purpose. This must mean it had a designer – a watch maker. Paley then points out there are also things in the universe that are complex and have a purpose. He points out in particular the complexity of the Human eye which is arranged to fulfil the purpose of enabling us to see. He also points to the wings of a bird and fins of a fish which are examples of complexity fitted together to perform a purpose of flying and swimming.
“Every manifestation of design, which existed in the watch, exists in the works of nature.”
Since complexity and purpose in a watch tells us there must have been a watch maker, similarly the complexity and purpose in the universe tells us that there must have been a universe maker: God.
Hume’s criticism of the use of analogy. Hume argues that it doesn’t follow from the similarity of two effects that they must have had similar causes. The smoke produced by fire and dry ice is very similar, but their causes not similar. So, just because the effect of the watch and the effect of the universe are like each other in that they both have complexity and purpose, it doesn’t follow that the cause of the watch (a watchmaker) must be like the cause of a universe. Two effects which are alike (analogous) might in fact have very different causes.
Hume argues further that any analogy between artefacts (man-made things) and natural things in the universe is faulty. He gave the example of a house but it applies to Paley’s watch too. This is because the universe is not like a machine (whereas a watch or house is) at all since it is composed of living things, it is more organic than it is mechanical.
Paley’s argument is arguably not based on an analogy. Modern philosophers tend to read Paley’s argument as not being based on an analogy between artefacts and the universe. His argument is that there is a property which requires a designer; the property of complexity and purpose – parts fitted together in a complex way to perform a purpose. When a complex of individually complex parts are fitted together in a meticulous way so as to achieve an overall function/purpose, it seems almost impossible for that to have come about by pure chance. A better explanation is a designing mind. Man-made things have this property but so too do natural things like the eye. Therefore, nature requires a designer because it has this property, not because of any analogy to man-made things. The watch is merely an illustration. We know the universe is designed because it has complexity and purpose.
Hume: the teleological argument is arguing from a unique case. Hume challenges the idea that we could possibly know that complexity and purpose must be caused by a designer in the case of the universe. Hume argues that the only way to know the cause of something is to have empirical evidence or experience of that cause. We have not experienced universes being made so cannot know what their cause was. Nor do we have examples of designed universes and non-designed universes to compare our universe to. All we have is one case – one universe. We thus lack the required empirical evidence to judge whether our universe was designed.
“A very small part of this great system, during a very short time, is very imperfectly discovered to us; and do we thence pronounce decisively concerning the origin of the whole?” – Hume.
Hume’s argument doesn’t apply to the watch. Paley’s argument rests on the premise that we know a watch is designed by its complexity and purpose. Arguably a person could come across a watch and would know it was designed, even if they had never seen watching being made or even heard of how they were made. So, it looks like Paley is right that someone can know something is designed by its complexity and purpose, and that Hume is wrong to think that experience of the causal process that originated it is required to know whether it was designed.
Actually it does. However, Hume’s point is that even if someone got the correct idea that a thing is designed by observing its complexity and purpose, they actually don’t have justified knowledge. It’s possible for someone to get a correct idea through unjustified means. Paley could even be right that complexity and purpose is the feature of the watch that tempts us to the conclusion that it was designed, but that doesn’t justify the belief that the watch was designed. Even though the belief be true, it may be false for anything they know, because they lack justification. The only way to know a watch is designed is to see it being made.
Hume: God is not the only explanation. Hume argues that even if we had evidence of design in the universe, that would not support the claim that it was designed by the God of classical theism. It could have been made by a junior God, apprentice God – or even a God who died. There could be multiple designers – ‘a committee of Gods’. So, the design argument doesn’t even justify monotheism.
Swinburne claims that Hume’s points here are correct and that the design argument cannot prove that the designer has the attributes of the God of classical theism. Other arguments will be needed for that.
However, Swinburne thinks that Ockham’s razor can be used against some of Hume’s claims here. One God being responsible for the design of the universe is a simpler explanation than multiple. Swinburne also points to the uniformity of the laws of physics as suggesting a single designer.
Hume’s evidential problem of evil can be used against the design argument. Hume aims to show that a posteriori observation of the world cannot provide a basis to conclude that a perfect God exists because the world contains imperfections like evil. Hume isn’t trying to prove that there is no designer, just that a posteriori evidence cannot be used to show that the designer must be the God of classical theism (omniscient, omnibenevolent, omnipotent).
‘I … allow, that the bad appearances, notwithstanding all my reasonings, may be compatible with such attributes as you suppose: But surely they can never prove these attributes’
Hume, as an empiricist, insists that we are only justified in believing what the evidence suggests. The evidence of an imperfect world, while logically compatible with a perfect God, can never justify belief in a perfect God.
Paley responds that even a broken watch must have a watch maker, and so too must it be with the universe.
Alternative response to Hume’s evidential problem of evil: theodicies.
Paley: design qua regularity.
Design qua Regularity is another type of design argument made by Paley which draws on the observation of the order found in Newtonian physics. Paley pointed to the rotations of planets in the solar system and how they obey the same universal laws as shown by Newton’s laws of motion and gravity. Paley argued that unless gravity consistently has the strength it does within a narrow boundary, then the planets would be unable to maintain their order and life on earth could not exist. Similarly, why is the universe regular and not chaotic? This could not have come about by chance.
Hume’s Epicurean hypothesis can be used to criticise Paley, especially design qua regularity. Epicures was an ancient Greek philosopher who thought the universe was had existed infinitely and was composed of atoms. Hume pointed out that if Epicures was correct, then a chaotic random universe, given an infinite amount of time, will by complete chance occasionally assemble itself into an orderly one. The atoms will happen to collide in such a way that an orderly arrangement of them will come about. On an infinite time scale, if something can possibly happen then no matter how low the probability, it becomes 100% guaranteed to happen. Not just once, but an infinite number of times! For example if monkeys were randomly banging away on typewriters for an infinite amount of time, then they would produce the entire works of Shakespeare. Similarly, a chaotic universe of randomly moving and fluctuating objects will happen to coalesce into an orderly arrangement given an infinite time frame.
Defence of design qua regularity: Currently the view of science is that time began at the big bang however, therefore there has not been an infinite amount of time.
Counter-defence: Perhaps there were infinite universes before ours or an infinite number of universes (multiverse theory). Rather than a regular universe occurring by chance due to an infinite time-frame, instead it could be that a regular universe occurred by chance due to there being an infinite number of every type (regular and chaotic) of universe.
Swinburne’s defence: However, there is very little evidence for the multiverse theory. Polkinghorne agrees and claims that the multiverse theory is a ‘bold speculation’, a ‘metaphysical guess’.