The crux of Stephen Meyer’s argument in Signature in the Cell can be succinctly summarized in this syllogism:
1. DNA information is complex specified information (CSI)
2. All complex specified information is generated by intelligent beings
3. Therefore, DNA information was generated by an intelligent agent
The first sentence is amply documented in his book following the definitions laid out over the years in ID books by Dembski and others. The second statement deserves a little more attention.
Meyer emphasizes the close relationship between DNA information and information such as computer code that is generated by human intelligent agents. On page 386 he states “Although a computer program may be similar to DNA in many respects and dissimilar in others, it exhibits a precise identity to DNA insofar as both contain specified complexity or specified information.” Throughout the book, Meyer repeatedly notes that specificity of information can be of two types, either deriving its specificity from functionality or else from meaning. Thus, there are at least two distinct subsets of information within the category of CSI. Accordingly, on page 359, Meyer titles one of his subsections “Two Types of Specifications.”
On page 109 Meyer states that DNA information is of the functional type. “Although DNA does not convey information that is received, understood, or used by a conscious mind, it does have information that is received and used by the cell’s machinery to build the structures critical to the maintenance of life. DNA displays a property–functional specificity—that transcends the merely mathematical formalism of Shannon’s theory.” Computer code is information that is used by a conscious mind. Hence, while a computer program and DNA information may be identical in being specified complex information, they differ in the type of specificity. This is significant with regard to its source.
Meyer presents many examples throughout the book to show that CSI can only come from an intelligent source. He might have strengthened his case by adding a deductive argument to his inductive approach. One of the characteristic traits of intelligence is the ability to do abstract reasoning. Abstractly-designed information, the “meaning” type of CSI, is therefore uniquely derived from an intelligent source. Had he done so, he might have noticed, however, that “functional” CSI is not in the group uniquely sourced from intelligence. Indeed, all of the examples that Meyer cites relate to information that derives its specificity at least partially from meaning and not solely from functionality. The latter depends on the physical and chemical structure of the system conveying the information while the former, which includes systems with a combination of meaning and function, depends on abstraction beyond the concrete reality.
As Meyer pointed out, DNA information is functional information, distinct from the meaning type of information. Since only the latter is known to be uniquely sourced from intelligence, it cannot be inferred that DNA information could only arise from an intelligent agent.