The Design Argument Critiqued

Cleanthes' design argument proceeds by analogy: as a machine is to its maker, so the universe is to its creator. But Philo argues that this analogy is far too weak to support its conclusion. A good analogical inference requires that the cases compared be sufficiently similar and numerous. The universe is unique — we have only one of it, we have never observed another universe being created, and we cannot compare this universe's origin with the origin of others. The comparison with machines rests on our experience of the human world, which is a tiny and possibly unrepresentative sample of nature as a whole. The more the universe differs from a machine, the weaker the inference to a machine-like cause.

Philo presses the point by noting that, even within our experience of organised complexity, intelligent design is not the only possible explanation. Vegetation and animal generation also produce complex, ordered structures without planning. If we are to argue from observed effects to their most probable cause, we might equally well infer that the world was generated or grown rather than made. There is no reason, given the evidence alone, to prefer the analogy with human artifice over the analogy with biological generation or the analogy with the self-organising physical processes revealed by Newtonian science.

Even granting the inference to an intelligent designer, Philo argues that the argument tells us almost nothing about the designer's nature. The cause need only be proportioned to its effects: a finite world requires at most a finite designer; an imperfect world suggests at most an imperfect designer; a world made by trial and error suggests at most a designer who learned by attempting many worlds before getting this one approximately right. The argument provides no grounds for the attributes traditional theology requires — infinite power, infinite goodness, unity, or concern for human welfare. It is at best evidence for some designer more powerful than human beings; it is not evidence for the God of any religious tradition.

The critique of the design argument occupies Parts II–VIII of the Dialogues, with Philo developing increasingly devastating objections to Cleanthes' position. The Dialogues were composed over several decades and revised repeatedly; the dramatic irony of the final section — where Philo appears to recant — has been debated by scholars since publication. The influence on Kant's critique of the physico-theological proof in the Critique of Pure Reason and on Darwin's naturalistic explanation of biological design is extensive.