Editor’s note: We are delighted to welcome the new and greatly expanded second edition of The Design Inference, by William Dembski and Winston Ewert. The following is excerpted from the Introduction.

Darwinian critics, however much they were willing to permit design inferences in other contexts, reflexively ruled them out as soon as they impacted biology or cosmology or anyplace where a non-natural designer might be implicated. They thereby gutted the design inference of any larger worldview significance, ensuring that it could never be applied to humanity’s really big and important questions.

Early in The Blind Watchmaker, Richard Dawkins stated that life is special because it exhibits a “quality” that is “specifiable in advance” and “highly unlikely to have been acquired by random chance alone.” All the elements of specified complexity are there in Dawkins’s characterization of life. Yet Dawkins, along with fellow Darwinians, did not see in specified complexity a marker of actual design but rather the outworking of natural selection, naturalism’s great designer substitute. For Dawkins, natural selection removes the small probabilities needed to make the design inference work. As he remarks, the “belief, that Darwinian evolution is ‘random,’ is not merely false. It is the exact opposite of the truth. Chance is a minor ingredient in the Darwinian recipe, but the most important ingredient is cumulative [i.e., natural] selection, which is quint- essentially nonrandom.” Nonrandom here means, in particular, not all that improbable.

Two Conditions for a Design Inference

For a design inference to properly infer design, two conditions must be met:

1. an observed outcome matches an independently identifiable pattern, or what we call a specification (what Dawkins means by “specifiable in advance”); and
2. the event corresponding to that pattern has small probability (think of the pattern as a target and an arrow landing anywhere in it as the corresponding event).

With these conditions satisfied, the design inference ascribes such an observed outcome to design. Dawkins finds no fault with this form of reasoning provided the probabilities are indeed small. He even admits that scientific theories are only “allowed to get away with” so much “sheer unadulterated miraculous luck” but no more. Dawkins is here expressing the widespread intuition that certain events are within the reach of chance but that others are not. He’s right that people widely embrace this intuition, and he’s right that this intuition applies to science.

Given his view that scientific theorizing can only permit a limited amount of luck (a view ID proponents share), Dawkins would be forced to concede that if randomness were operating in the evolution of life, the resulting probabilities would be small, and a design inference would be warranted. As evidence that Dawkins does indeed make this concession, consider the way he commends William Paley’s design argument. In a remarkable moment of candor, Dawkins writes, “I could not imagine being an atheist at any time before 1859, when Darwin’s Origin of Species was published… [A]lthough atheism might have been logically tenable before Darwin, Darwin made it possible to be an intellectually fulfilled atheist.” According to Dawkins, but for Darwin, we would be stuck with Paley and compelled to be theists.

Breaking Intelligent Design

Darwin, in positing natural selection as the driving force behind evolution, was thus seen as breaking the power of classical design arguments. Natural selection, with its ability to heap up small incremental improvements, would allow evolution to proceed gradually, baby step by baby step, overcoming all evolutionary obstacles. In proceeding by baby steps, Darwinian evolution is supposed to mitigate the vast improbabilities that might otherwise constitute insuperable obstacles to life’s evolution, substituting at each step probabilities that are eminently manageable (not too small).

Darwinian processes, by overcoming probabilistic hurdles in this way, are thus said to banish design inferences from biology. The actual small probabilities needed for a valid design inference, according to Dawkins and fellow Darwinian biologists, thus never arise. Indeed, that was Dawkins’s whole point in following up The Blind Watchmaker with Climbing Mount Improbable. Mount Improbable only seems improbable if you have to scale it in one giant leap, but if you can find a gradual winding path to the top (baby step by baby step), getting there is quite probable.

Dawkins never gets beyond such a broad-brush description of how vast improbabilities that might otherwise dog evolution can be mitigated. As it is, there are plenty of probabilistic situations in which each step is reasonably probable but the coordination of all these reasonably probable events contributes to an outcome that is highly improbable. Flip a coin a hundred times, and at each flip the coin is reasonably likely to land on heads. But getting a hundred heads in a row is highly improbable, and we should not expect it to happen by chance. Dawkins doesn’t just need reasonably sized probabilities at each step, but a kind of coordination or ratcheting that locks in prior benefits and keeps striving for and accumulating future benefits. Showing that natural selection possesses this power universally goes well beyond what he, or any other Darwinian biologist, ever established probabilistically.

Confusing Apparent with Actual

In short, Darwinian critics of the design inference conflate apparent specified complexity with actual specified complexity. Darwinists like Dawkins grant that actual specified complexity warrants a design inference. But they view the Darwinian mechanism of natural selection as a probability amplifier, making otherwise improbable events probable and thus rendering them no longer complex. As a consequence, it does not matter that specified complexity, as a matter of statistical logic, warrants a design inference because, according to Darwinists, life does not actually exhibit specified complexity. Darwinists will, to be sure, claim that the Darwinian mechanism creates specified complexity. But what they really mean is that the Darwinian mechanism causes life to exhibit the illusion of specified complexity. Living systems only seem to be highly improbable, but they’re not once you understand how Darwinian evolution brings them about. In this way, the majority of evolutionary biologists, insofar as they understand the design inference at all, rationalize it away.

Since the publication of the first edition of this book, the debate over the design inference and its applicability to evolution has centered on whether such gradual winding paths exist and how their existence or non-existence would affect the probabilities by which Darwinian processes could originate living forms. Design theorists have identified a variety of biological systems that resist Darwinian explanations and argued that the probability of such systems evolving by Darwinian means is vanishingly small. They thus conclude that these systems are effectively unevolvable by Darwinian means and that their existence warrants a design inference. In this book, we recap that debate and contend that intelligent design has the stronger argument.