What is intelligent design, and is it science?

Intelligent design (ID) is the claim that “certain features of the universe and of living things are best explained by an intelligent cause, not an undirected process such as natural selection”^{[source 1]}. Its leading proponents, many of them fellows of the Discovery Institute’s Center for Science and Culture, include the philosopher of science Stephen Meyer, the biochemist Michael Behe and the mathematician and philosopher William Dembski.

Proponents distinguish ID from creationism. It makes no claim about the age of the earth or the identity of the designer, and Meyer writes that it does not challenge evolution as change over time, or even common ancestry; what it disputes is that the cause of biological change is wholly blind and undirected^{[source 2]}. Meyer traces the modern argument to The Mystery of Life’s Origin (1984), in which Charles Thaxton and colleagues argued that the information-bearing properties of DNA pointed to a designing intelligence^{[source 2]}.

ID reasons by inference to the best explanation. Dembski argued that design can be detected when an event is both highly improbable and matches an independently given pattern, a combination he called specified complexity^{[source 4]}. Proponents apply this to the information in DNA, to molecular machines that seem to need all their parts at once, to the sudden appearance of animal body plans in the Cambrian, and to the fine-tuning of physical constants. Because intelligent agents are known to produce such features, they argue, and no undirected process is known to, design is the better explanation^{[source 2]}.

Proponents insist the argument is positive, not merely a gap in current theories. Meyer writes that design theorists argue for design not only because chance, natural law or the two together have failed to explain certain features, but because “we know from experience that systems possessing these features invariably arise from intelligent causes”^{[source 2]}. On this view, inferring design from biological information is no different in kind from an archaeologist inferring a carver from an inscription, or the search for extraterrestrial intelligence treating a coded radio signal as the work of a mind^{[source 2]}.

The Discovery Institute describes ID as “a scientific theory that employs the methods commonly used by other historical sciences”^{[source 1]}. Geology, archaeology and forensic science all reason from present evidence to past causes they cannot observe directly, by asking which cause known to operate today best accounts for what is found. Proponents argue that ID applies the same reasoning to biology, and Meyer attributes its rejection to a “metaphysical prejudice” rather than to the evidence^{[source 2]}.

The central scientific objection is that ID offers no mechanism or testable predictions of its own: its arguments point to what evolutionary theory has not explained and conclude design. In Kitzmiller v. Dover Area School District (2005), after a six-week trial with expert witnesses on both sides, federal judge John E. Jones III found that ID “is at bottom premised upon a false dichotomy, namely, that to the extent evolutionary theory is discredited, ID is confirmed”^{[source 3]}. Proponents reply that ID’s arguments do make testable claims, and note that the court itself accepted that irreducible complexity, though not ID as a whole, can be tested^{[source 3]}.

Critics answer that the analogy with archaeology fails at the crucial point. The Kitzmiller court noted that for human artifacts “we know the designer’s identity, human, and the mechanism of design,” from direct experience of people making such things, and that no comparable knowledge exists for a designer of living things^{[source 3]}.

Critics also contest each specific argument, as the related questions describe, and scientific bodies have rejected ID as science. In 2002 the American Association for the Advancement of Science resolved that “the lack of scientific warrant for so-called ‘intelligent design theory’ makes it improper to include as a part of science education”^{[source 5]}.

Philosophers who study design arguments note a long-standing difficulty with arguments of this kind: much of their historical persuasiveness came from the absence of any known natural explanation, and when such explanations appear, the argument loses its force^{[source 6]}. Critics see the same pattern in ID. Proponents reply that they argue from what is known about the causes of information and machinery, not from what is unknown^{[source 2]}.

A further objection concerns ID’s origins. Comparing drafts of the ID textbook Of Pandas and People from before and after the Supreme Court’s 1987 ruling against teaching creationism as science, the Kitzmiller court found that the early drafts’ definition of creation science was identical to the later definition of ID, and that the words creationism and creationist, used about 150 times, had been systematically replaced^{[source 3]}. Proponents answer that a theory’s history does not decide whether it is true, and that ID’s claims differ from creationism’s^{[source 2]}.

ID has not been accepted as science by the major scientific organizations, and the Kitzmiller ruling barred teaching it in that district’s public-school science classes^{[source 3][source 5]}. Its proponents point to work they have published in peer-reviewed journals and monographs^{[source 1]}, and argue that its rejection reflects a definition of science that excludes design in advance. A few philosophers who are not theists, such as Bradley Monton, have argued that ID deserves a hearing as science even if its conclusions turn out to be false^{[source 7]}.

Whether nature shows evidence of design is one of the oldest questions in philosophy, and the arguments remain under active discussion^{[source 6]}. Whether ID’s particular arguments count as science, philosophy or theology is itself contested, including among Christians, many of whom accept evolution and see God’s purposes at work through natural processes^{[source 6]}.