Evolution Icon Evolution
Intelligent Design Icon Intelligent Design

The Logic of Design Detection

Photo: The Rosetta Stone, by ProtoplasmaKid, CC BY-SA 4.0 , via Wikimedia Commons.

Editor’s note: This article is an excerpt from a chapter in the newly released book The Comprehensive Guide to Science and Faith: Exploring the Ultimate Questions About Life and the Cosmos. We are presenting Dr. Meyer’s chapter as a series, in which this is the third post. Find the full series so far here.

In The Design Inference, mathematician William Dembski explicates the logic of design detection. His work reinforces the conclusion that the specified information present in DNA points to a designing mind. 

Dembski shows that rational agents often detect the prior activity of other designing minds by the character of the effects they leave behind. Archaeologists assume that rational agents produced the inscriptions on the Rosetta Stone. Insurance fraud investigators detect certain “cheating patterns” that suggest intentional manipulation of circumstances rather than a natural disaster. Cryptographers distinguish between random signals and those carrying encoded messages, the latter indicating an intelligent source. Recognizing the activity of intelligent agents constitutes a common and fully rational mode of inference.

High Complexity and Specification

More importantly, Dembski explicates criteria by which rational agents recognize or detect the effects of other rational agents and distinguish them from the effects of natural causes. He demonstrates that systems or sequences with the joint properties of “high complexity” (or small probability) and “specification” invariably result from intelligent causes, not from chance or physical-chemical laws.1 Dembski notes that complex sequences exhibit an irregular and improbable arrangement that defies expression by a simple rule or algorithm, whereas specification involves a match or correspondence between a physical system or sequence and an independently recognizable pattern or set of functional requirements. 

By way of illustration, consider the following three sets of symbols:

  • “nehya53nslbyw1`jejns7eopslanm46/J”

The first two sequences are complex because both defy reduction to a simple rule. Each represents a highly irregular, aperiodic, improbable sequence. The third sequence is not complex, but is instead highly ordered and repetitive. Of the two complex sequences, only the second, however, exemplifies a set of independent functional requirements — i.e., it is specified

How Communication Occurs

English has many such functional requirements. For example, to convey meaning in English, one must employ existing conventions of vocabulary (associations of symbol sequences with particular objects, concepts, or ideas) and existing conventions of syntax and grammar. When symbol arrangements “match” existing vocabulary and grammatical conventions (i.e., functional requirements), communication can occur. Such arrangements exhibit “specification.” The sequence “Time and tide waits for no man” clearly exhibits such a match, and thus performs a communication function.

Thus, of the three sequences, only the second manifests both necessary indicators of a designed system. The third sequence lacks complexity, though it does exhibit a simple periodic pattern, a specification of sorts. The first sequence is complex, but not specified. Only the second sequence exhibits both complexity and specification. Thus, according to Dembski’s theory of design detection, only the second sequence implicates an intelligent cause — as our uniform experience affirms.

A Scientific Method of Design Detection

In my book Signature in the Cell, I show that Dembski’s joint criteria of complexity and specification are equivalent to “functional” or “specified information.” I also show that the coding regions of DNA exemplify both high complexity and specification and, thus not surprisingly, also contain “specified information.” Consequently, Dembski’s scientific method of design detection reinforces the conclusion that the digital information in DNA indicates prior intelligent activity. 

So, contrary to media reports, the theory of intelligent design is not based upon ignorance or gaps in our knowledge, but on scientific discoveries about DNA and on established scientific methods of reasoning in which our uniform experience of cause and effect guides our inferences about the kinds of causes that produce (or best explain) different types of events or sequences. 

Next, “Anthropic Fine-Tuning as Evidence of Design.”


  1. William A. Dembski, The Design Inference: Eliminating Chance Through Small Probabilities (Cambridge, MA: Cambridge University Press, 1998), 36-66.