3.3.2 - Problems for design arguments

The Design Inference Under Pressure

Design arguments begin from an ordinary habit of thought. If you find something whose parts are arranged for a purpose, you often infer that it was produced by intelligence. A watch, a telescope, a library catalogue, or a well-ordered machine does not look as if its useful structure is accidental. The design argument asks whether the same style of reasoning can move from order or purpose in nature to God.

This lesson is not mainly a lesson on constructing design arguments. It is a lesson on the pressure points. The AQA issue is whether the inference from order to God survives Hume's objections, the presence of spatial disorder, the fact that the universe is a unique case, and rival explanations of order.

Key vocabulary:

A simplified target argument looks like this:

1. P1: The world contains order, purpose, or regularity.
2. P2: In familiar cases, order, purpose, or regularity of this kind is produced by intelligence.
3. P3: Similar effects probably have similar causes, or the best explanation of such order is intelligence.
4. P4: God is the best or only intelligent cause able to explain the world's order.
5. Therefore, C: The order in the world gives strong support to God's existence.

Hidden assumption: The order in nature is relevantly like order in human artefacts, and rival natural explanations do not explain it better.
Inference type: Inductive, analogical, or abductive, depending on the version.
Main pressure point: P4, because even if design is inferred, it may not establish the God of classical theism.

This matters for evaluation. Do not criticise the design argument by saying that it is not deductively valid. Most design arguments are not meant to be deductive proofs. The better question is whether the evidence makes God probable, or whether Humean and natural explanations make the inference too weak.

The AQA set-text boundary is also important:

Hume On Weak Analogy

Hume's Dialogues presents the design argument through Cleanthes. Cleanthes argues that the world resembles a great machine: its parts are adjusted to one another, and this resembles human contrivance. Since similar effects suggest similar causes, he infers that the cause of nature is somewhat like human intelligence.

Philo's reply targets the analogy itself. An analogical argument is strong only when the compared cases are similar in the relevant respects and when we already have experience linking that kind of effect with that kind of cause. We have repeated experience of houses, ships, watches, and machines being produced by human designers. We do not have repeated experience of universes being produced by divine minds.

The objection can be reconstructed like this:

1. P1: An analogical inference is strong only when the compared effects are relevantly similar and the cause-effect connection is supported by experience.
2. P2: Human artefacts and the whole universe are not relevantly similar enough: artefacts are small parts of the world, while the universe is the whole system.
3. P3: We have experience of artefacts being made, but no experience of universes being made.
4. Therefore, C: The design argument from analogy is weak.

Hidden assumption: The whole universe cannot be treated as just another item in the same class as human artefacts.
Inference type: Critical analysis of analogical reasoning.
Main pressure point: P2, because defenders can argue that the relevant similarity is not size or material, but purposeful arrangement.

This is not the crude objection that the universe is not exactly like a watch. No analogy requires exact sameness. The point is about relevant similarity. A watch has parts arranged to tell the time, and we already know watches are made by human minds. The universe contains many ordered structures, but it is not obviously a product in the same way. The design argument needs to show that the similarity is strong enough to support a similar cause.

Hume also presses the modesty of the conclusion. If the analogy is with human designers, the cause inferred should be proportioned to the effect and to the analogy. Human designers are finite, embodied, limited, sometimes mistaken, and often collaborative. So even if the analogy supported some designer-like cause, it would not automatically support an infinite, omnipotent, omniscient, omnibenevolent, single God.

The main reply is to refine the argument. Paley can say that he is not relying on a loose resemblance between nature and watches, but on a specific feature: functional arrangement of parts for an end. Swinburne can say that the argument is better treated as an explanatory hypothesis rather than as a simple analogy. A defender of these probabilistic readings concedes that the inference is not a deductive proof, but insists that it can still provide support. A deductive Paley reading instead needs to defend the universal premise that purposive contrivance implies design.

The residual issue is that the reply changes the burden of proof. The defender must show that the relevant feature really is a reliable sign of intelligence when found in nature, not only when found in human artefacts.

Spatial Disorder

Spatial order is arrangement at a time. Paley's watch is spatially ordered because its parts are arranged so that they work together to tell the time. Paley's examples from the eye and living organisms also depend on spatial order: lenses, muscles, nerves, bones, and organs are arranged in ways that seem useful.

The problem of spatial disorder asks why the design argument is allowed to count order as evidence for God while discounting disorder. The world contains many ordered arrangements, but it also contains irregularity, waste, malfunction, apparent poor design, chaotic arrangement, disease, predation, and parts whose purpose is unclear. If order supports a wise designer, disorder seems to weaken that support or suggest a limited designer.

The objection can be reconstructed like this:

1. P1: If spatial order is evidence for an intelligent and good designer, spatial disorder is evidence against such a designer, or at least against a perfect designer.
2. P2: The world contains both spatial order and spatial disorder.
3. P3: A design argument that counts only the order and ignores the disorder is selective.
4. Therefore, C: Spatial order alone does not clearly support the God of classical theism.

Hidden assumption: Evidence for design must take the whole pattern of order and disorder into account.
Inference type: Evidential objection to explanatory strength.
Main pressure point: P1, because defenders may deny that imperfection removes evidence of design.

Hume's pressure is especially damaging when the conclusion is ambitious. If the design argument claims to prove a perfect God, then faults, suffering, waste, or clumsy arrangement matter. On Hume's own principles, like effects suggest like causes. A mixed and imperfect world may suggest a mixed, limited, or imperfect cause rather than a perfect one. It might even fit several designers, a novice designer, or a designer whose purposes are not benevolent.

Paley has a direct reply. A machine does not need to be perfect in order to show design. A watch that sometimes goes wrong can still plainly be a watch made for a purpose. Unknown parts or even apparently useless parts do not cancel the evidence supplied by parts whose function is clear. Paley's point is that design can be inferred from positive signs of contrivance even when not every feature is understood.

That reply has force. A broken clock can still be designed. A biological organ might show striking functional arrangement even if other parts of nature look messy. Spatial disorder therefore does not automatically destroy every design inference.

The residual issue is the size of the conclusion. Paley's reply may defend the claim that some design-like arrangement exists, but it does not by itself establish that the designer is perfect, all-good, or all-powerful. Swinburne adds a different lesson: arguments from spatial order are vulnerable because some spatial order may be explained through ordinary natural processes, such as biological development and evolution operating under laws of nature. That is why Swinburne thinks a stronger design argument should focus more on temporal order, the regular operation of natural laws, than on spatial arrangements alone.

Unique Case Objection

The unique case objection is easy to blur with the analogy objection, but it is sharper. The analogy objection says the universe is not sufficiently like artefacts. The unique case objection says that the universe, considered as a whole, is the only case of its kind available to us. We cannot compare this universe with many other universes, some known to be designed and some known not to be designed. Nor have we observed worlds being made.

Ordinary design inferences usually rely on a background comparison class. We know that watches, houses, books, and machines are made by intelligent agents because we have wider experience of such things. With the whole universe, Hume argues, that background is missing.

1. P1: Reliable empirical inference normally depends on a comparison class or repeated experience linking a type of effect with a type of cause.
2. P2: The origin and order of the universe as a whole is a unique case for us.
3. P3: We have no observed sample of universe-making from which to infer the cause of this universe.
4. Therefore, C: We cannot confidently infer a divine designer from the universe as a whole.

Hidden assumption: A cause of the whole universe cannot be inferred from experience of causes within the universe.
Inference type: Humean challenge to induction and analogy.
Main pressure point: P1, because defenders can argue that some one-off inferences are still rational.

A design defender can reply that not all good inferences require repeated observation of exactly the same kind of case. Scientists and historians often infer unobserved causes from traces, even when the event is not repeatable. A detective may infer a crime from one scene; an astronomer may infer an unobserved body from its effects; a physicist may infer an entity from its explanatory role.