Intelligent design

Intelligent design (ID) is the designation for a claim that certain fundamental features of the universe and living things are best explained by purposeful causation—a "higher intelligence."

Proponents of ID point to examples in the natural world, such as living organisms, whose origins, in their view, are the result of the intervention of a higher intelligence, rather than by chance interactions. For mainstream biologists, such claims are not supported by evidence in the scientific literature and when intelligent design claims have been put to a rigorous test an evolutionary explanation provides an adequate explanation for the diversity of related structures.

See intelligent design movement for an account of the efforts to employ ID to rebut evolution to better promote education about intelligent design within schools.

An Argument for Intelligent Design

The classic design argument for the existence of an intelligent creator may be traced from ancient philosophy, through the works of medieval scholastics such as the philosopher-theologian Saint Thomas Aquinas(1225-1274), who argued that the existence of God could be deduced by reason.

In the 19th century, William Paley (1743-1805) introduced the "watchmaker analogy", one of the best known metaphors in the philosophy of science, as an argument for the existence of God. The argument is, in essence, as follows: Imagine walking on a pebbled beach, where the pebbles may be wonderfully shaped, beautiful in different ways, interesting and varied one from another. However interesting and beautiful you find them, you will not doubt that they are the products of purely natural causes. However, if amongst the pebbles you find a watch, even if you have never seen a watch before, you will immediately recognise it as qualitatively different from the pebbles. Inspecting it, from the intricacy of its design, and the clear purpose of that design, you will inevitably and correctly conclude that the watch is not a 'natural' object but an artifact, something designed by a powerful and intelligent agent.

Casual observation might similarly lead to the conclusion that, compared to a watch, even the simplest living form is incredibly complex, giving it the appearance of being designed for a purpose. There must be a designer, said Paley, and that designer is God.

The currently accepted account of the origin of living things is known as the "Modern Evolutionary Synthesis", a theoretical framework which expresses the theory of evolution by natural selection in a form consistent with molecular biology and population genetics. By this theory all extant living things are the products of descent with modification from common ancestors that lived 3-4 billion years ago. This theory explains all evolution as resulting from processes of natural selection among populations that vary in a random way (as a result of spontaneous genetic mutations, and of random shuffling of genes in the offspring of sexually reproducing species). Natural selection is a creative process because, as favorable mutations accumulate over generations and combine in different ways, this produces a huge diversity of organisms - more than 10 million living species.

There are important features that distinguish the 'design' achieved by natural selection from the kind produced by an intelligent designer. Natural selection is undirected in that it has no preordained plan, but is simply a result of the differential survival and reproduction of living beings. Natural selection has no foresight, and so environmental changes may threaten the survival of organisms that werethriving. As a result, species extinction is common: it is estimated that "more than 99% of all species that have ever lived on Earth are now extinct."

Modern proponents of intelligent design argue that evolution by an 'undirected' process like natural selection cannot adequately account for the complexity of life. They argue that essential features of even the simplest extant living things are 'irreducibly complex', in that such features arise only in highly complex systems and do not appear in even a rudimentary form in simple systems. They argue that an irreducibly complex system is very unlikely to be produced by successive, slight modifications of a previously existing system, because any precursor that was missing a crucial part would be unable to function at all.

It has not been possible to reconstruct in reliable detail the events that gave rise to the simplest form of life; there is too much that remains unknown. Accordingly, intelligent design theory argues that it is just as appropriate to postulate an intelligent agent to explain the mysteries of life as it is to postulate an intelligent watchmaker to explain the watch found on a beach.

Some ID proponents consider that alternative explanations (including Darwinian evolution) are not feasible, as they argue that the well-documented natural selection mechanisms that have been used to explain the "apparent design" of numerous components and interactions of living organisms cannot explain all features of organism complexity. They see evolution as an "undirected, chance-based process"; ID does not emphasise that selection for reproductive success intrinsically directs evolutionary change towards functional design solutions, or that numerous genetic mechanisms exist to provide a vast array of genetic diversity from which well designed components can be selected.

Irreducible Complexity

One of the central arguments used by proponents of intelligent design involves the concept of 'irreducible complexity'. These proponents argue that irreducible complexity is a common feature of biological systems, but cannot plausibly be accounted for by evolution through 'undirected' natural selection. They argue instead that irreducibly complex systems must have arisen by some form of 'directed' evolution, i.e. towards a predetermined end.

A complex system is a system that performs a discrete function, where there are many interactions between its component parts. A system is irreducibly complex if removing of any one of the parts of a complex system causes it to effectively cease functioning.

In No Free Lunch, William Dembski extends this basic definition, and states that a system is irreducibly complex

"if it includes a set of well-matched, mutually interacting, non-arbitrarily individuated parts such that each part in the set is indispensable to maintaining the system's basic, and therefore original, function."

Contemporary and high profile proponents of intelligent design

Prominent ID proponent William Dembski has a PhD in mathematics from the University of Chicago, and is research professor in philosophy at Southwestern Baptist Theological Seminary in Fort Worth, Texas. In 1998, Cambridge University Press published Dembski's first book, a philosophical monograph entitled The Design Inference: Eliminating Chance through Small Probabilities. Dembski has published several books since, but has published no papers on intelligent design in the peer-reviewed scientific literature. Dembski is particularly associated with the concept of 'specified complexity'.

Another prominent proponent, and one particularly associated with arguments related to the concept of 'irreducible complexity', is Michael J. Behe. Behe is professor of biochemistry at Lehigh University in Pennsylvania. Behe holds that some biological structures are too biochemically complex to be plausibly explained as a result of evolution by natural selection. Unlike many in the intelligent design movement, Behe accepts the evidence for the common descent of species, including the conclusion that humans descended from other primates; however, he claims that common descent alone cannot fully explain the differences between species.

Both Dembski and Behe are senior fellows of the Discovery Institute's Center for Science and Culture in Seattle. The Discovery Institute is a Christian educational foundation established to promote creationist thought, founded by Stephen C. Meyer, Bruce Chapman and George Gilder. Meyer gained a Ph.D in history and philosophy of science from Cambridge University for a dissertation entitled "Of clues and causes : a methodological interpretation of origin of life studies."

The argument has been made that these proponents are not presenting scientific theory for the purpose of advancing science. Opponents have charged that the Discovery Institute and its fellows are using Intelligent Design as a wedge to drive their particular religious agenda into the public schools, where they hope to rebut the teachings and their perceptions about mainstream evolutionary science. Thus far the efforts of the Intelligent Design Movement have been unsuccessful due to their inability to craft an argument for intelligent design that mainstream science (and the courts) can recognize as scientific hypothesis or theory.

Distinct from creationism

Most proponents of the intelligent design hypothesis are also creationists, meaning they believe the universe was created by a deity or some other power beyond the comprehension of mortal man. The hypothesis, however, is not the same as young earth creationism, which is a belief that the account of the creation of the universe and of life as given by the Bible is literally true. Intelligent design does not try to identify the designer as supernatural, nor does it try to establish the veracity of a particular narrative, although some leading proponents of intelligent design have stated that they believe the designer to be the Christian God.

As intelligent design avoids identifying the designer, its focus is different to that of arguments in natural theology, such as the teleological argument. William Dembski argues that intelligent design can be formulated as a scientific theory of information that has empirical consequences and which is devoid of any religious commitments.[1] By this view, intelligent design asks whether design can be detected in nature from purely scientific and mathematical considerations.

Other proponents of intelligent design see no conflict between intelligent design and evolution, and indeed see evolution as evidence of intelligent design.

Criticisms of intelligent design

Both philosophical and scientific proponents of intelligent design argue that it is a scientific theory rather than a matter of religious belief, but many scientists reject this assertion. Mainstream scientists consider that for a theory to be 'scientific' it must generate predictions by which it can be tested; in other words it must be open to attempted disproof. For example, the philosopher of science Karl Popper argued that a theory that has no testable components "has no connection with the real world." As ID is not open to test, it is not a scientific theory in this sense (see Scientific method).

Scientists critical of intelligent design also dismiss the claim that only the intervention of a higher intelligence can adequately explain certain poorly understood phenomena; they do not regard such a lack of understanding as good evidence for any scientific conclusions. Intelligent design proponents respond, to the contrary, by claiming that the phenomena they take as evidence of intelligent design cannot be understood except by reference to a higher intelligence. Mainstream scientists, being concerned with understanding those phenomena in natural terms, naturally disagree.

Herein, we will detail some of the most common elements of the intelligent design narrative, but this criticism is by no means exhaustive or complete. So long as the basis of intelligent design remains an explanation for that which is not fully understood, then the refutation intelligent design will remain expansive but incomplete.

Critics hold that the postulate of an intelligent designer is not an explanation for life at all, but an evasion of attempted explanation. By this view, intelligent design has no content, and makes no predictions by which it can be tested. Some argue that the theory of evolution by natural selection, is also not really a testable scientific theory. For example, there is a detailed and coherent argument that accepts that "Darwinism" is scientifically invaluable, but also asserts that it is untestable, and should be regarded as a metaphysical platform for a research programme rather than a theory.

Opponents of intelligent design who are scientists consider that the evidence of complexity in biological systems can be explained by conventional biological theory. There are also many opponents of intelligent design who are religious, and who believe that the role of science is to seek natural, physical explanations of the world; although they believe that there is a God who created the world and life in it, for them this is a matter of faith not of science. Opponents of intelligent design doubt the intellectual honesty of intelligent design theory, in that they do not consider it to be a viable alternative to the theory of evolution by natural selection, and hence consider that the only reason for promoting it is for the religious message that it is said to contain, not for the intrinsic intellectual merits of the arguments.

The basic thesis of intelligent design that 'natural selection is undirected' is open to logical challenge. Natural selection of organism survival is indirectly specific on organism subcomponents, because many features of the subcomponents are determined by genes whose retention is determined by their importance for reproductive success of the organism. Organism survival selects for effective function of the organism sub-components as part of a coherently functioning whole. In any organism, survival places specific and subtle requirements and restrictions on particular components such as enzymes, sensors, organs and systems that interact to generate behavior of living things.

While proponents of intelligent design see evidence of design in how well complex structures fit their purpose, molecular biologists see something very different in the fine details of those structures. So far from seeing genetic information being perfectly and economically fashioned to suit a given purpose, they see wastefulness, duplication, errors, the detritus of now redundant genes in gene sequences - in other words, things they would expect to see as the residue of evolution by natural selection. In short, despite the appearance of efficient design at a high level, at a molecular level the design shows little sign of purposeful intelligence but extensive signs of chance processes.

Problems with the logic and assumptions of irreducible complexity

By the original common and uncontroversial definition many biological systems are irreducibly complex. However, conventional evolutionary theory has no intrinsic difficulty in explaining how a system can have arisen by natural selection and yet be irreducibly complex.

The key assumption which is problematic for Intelligent Design is the assumption introduced by Dembski that the basic function of a system is the same as its original function. This assumption is one that modern evolutionary biologists vigorously dispute. They claim that, on the contrary, systems often evolved for one purpose and then were "exapted" to a different function.

An example is the evolution of the wing. A small wing is useless for flying, so how could an aerodynamically effective wing ever have begun to evolve? The answer of evolutionary biologists is that small wings are indeed useless for flight but in insects, they are useful structures for thermoregulation - thus wings may have evolved for thermoregulation and increased in surface area to be more effective radiators of heat; while in mammals small wings can be used to increase running speed. The aerodynamic consequences would have been incidental to the original basic function, but when species had evolved wings of a sufficient size for gliding, then this originally incidental benefit may have become the major focus of further natural selection.

Another obvious way by which a system might become irreducibly complex is via the eliminative actions of natural selection. For example, genes that were once important in precursor forms of an organism are likely to be eliminated by natural selection if they later become redundant. Many see this as analogous to the scaffolding and buttresses that are used to construct a building and then removed after the building is completed, and therefore removing all evidence of the scaffolding. Thus in a currently living organism we see only the final structure - with little remaining evidence of the "scaffolds" by which evolution built it.

Another explanation is that genes used in an irreducibly complex system were once used for another purpose, much like melanocyte stimulating hormone (MSH), which acts as an antioxidant in organisms that don't produce melanin.

Michael Behe further adapted Dembski's definition to apply it to evolutionary pathways:

"An irreducibly complex evolutionary pathway is one that contains one or more unselected steps (that is, one or more necessary-but-unselected mutations)."

This step makes an overt link between irreducible complexity and intelligent design. As a definition, it can only be applied after assuming that evolution was directed (i.e. after assuming that there is any such thing as an unselected mutation)

Problems with assuming genetic mechanisms cannot produce intelligent design

An assumption in intelligent design is that genetic mechanisms cannot accomplish complex design outcomes, and that they are intrinsically random. Detailed modern genetics has, to the contrary, discovered mechanism by which organism have evolved mechanism to evolve rapidly in a quasi-directed fashion. Sexual reproduction is one of these, and Mobile DNAs are another.

The human immune system is a good illustration of the design capabilities of such genetic mechanisms. The creation of highly adapted antibodies that neutralise poisons and pathogens to which the body has never been previously exposed occurs by such natural selection events occurring in the cells of the immune system ( see Clonal Selection Theory of Acquired Immunity. Conversely pathogens use equally powerful genetic strategies ( such as sets of alternative genes for related structures) to evolve rapidly and to switch their antigenic features so as to evade the immune system.

The power of such quasi-intelligent systems is recognised by artificial intelligence engineers when they create software that expoits a genetic algorithm.

Could the flagellum have evolved by natural selection?

Critics of intelligent design argue that the idea that every piece of any biological machine must be assembled in its final form before anything useful can emerge is wrong. Evolution produces complex biochemical machines by copying, modifying, and combining proteins that were previously used for other functions. For example, Michael Behe argues that if you remove almost any of its parts, the bacterial flagellum does not work. However, it is argued by evolutionary theorists that many features of organisms evolved to fit one function and were then adapted through natural selection to fulfil a different function. By this view, natural selection is not a single path, but a multiply branching path with many dead ends, with many branching points where genes were duplicated, and with many changes of direction where the 'destination' changed. In other words, critics argue that the proponents of intelligent design misrepresent or misunderstand the processes involved in natural selection.

In particular, the flagellum is a structure that allows bacteria to move: 30 to 40 different proteins are required in a particular arrangement for the flagellum to work, and as it is argued that a flagellum is useless if it won't move, and needs all its parts to function, and that it is difficult to conceive that it arose by successive gradual mutations. This interpretation needs to account for the importance other genetic mechanisms in addition to mutation, and the evidence available from reconstruction of protein evolution by sequence comparisons. When the similarities among the different flagellum protein components are examined using this approach, it becomes clear that the modern day flagellum proteins evolved from just two precursors (a proto-flagellin and a proto-rod/hook protein) by multiple rounds of gene duplication and diversification. Relatives of some flagellum proteins are used in other bacterial structures. A protein that is similar to flagellum component FlgA is used in assembly of Type IV pili. Flagellum protein FlgJ contains region that digests the cell wall during flagellum insertion through the wall, and there are many bacterial proteins that are similar to it doing other tasks.

Thus some of the proteins from the flagellum are used by many bacteria for other functions as well, such as as a device for injecting poisons into other cells. Accordingly, biologists believe it is likely that different elements of the flagellum evolved separately to fulfil other functions in precursor organisms, and that motility arose relatively late in evolution, once many of the elements used in the flagellum were already in place for other reasons.

See also

• Intelligent Design? A special report reprinted from Natural History magazine. Three proponents of intelligent design present their views. Each view is followed by a response from a proponent of evolution. [2]
• Intelligent design movement