Intelligent design

Intelligent design (ID) is the designation for a claim that certain 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 that, in their view, can best be explained by 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, such as those concerning the bacterial flagellum, have been put to a rigorous test, an evolutionary explanation provides an adequate explanation for the diversity of related structures seen in living bacteria.

Intelligent design is presented by some proponents as scientific theory; most mainstream scientists disagree. 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 ID 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. ID proponents respond, to the contrary, by claiming that the phenomena they take as evidence of ID cannot be understood except by reference to a higher intelligence. Mainstream scientists, being concerned with understanding those phenomena in natural terms, naturally disagree.

See intelligent design movement for an account of the efforts to promote intelligent design within schools, and similar issues.

An Argument for Intelligent Design

The classic design argument for the existence of an intelligent creator may be traced to ancient philosophy, medieval scholastics (e.g., Aquinas) and early modern thought, such as the "watchmaker analogy" by William Paley. The premise of the argument is 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 lead to the conclusion that even the simplest living form is incredibly complex, giving it the appearance of being designed for a purpose. Proponents of intelligent design argue that natural selection and evolution do not 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

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.

By this common and uncontroversial definition, many biological systems are irreducibly complex. Conventional evolutionary theory has no intrinsic difficulty in explaining how a system can have arisen by natural selection and yet be irreducibly complex: one obvious way by which a system might become irreducibly complex is via the eliminative actions of natural selection. Genes that were once important in precursor forms of an organism are likely to be eliminated by natural selection if they later become redundant, thus in a currently living organism we see only the final structure - with little remaning evidence of the "scaffolds" by which evolution built it.

However, in No Free Lunch, ID proponent William Dembski 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." This form of the definition interposes a key assumption, 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 evoltion 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 are useful structures for thermoregulation - thus wings may have evolved for thermoregulation and increased in surface area to be more effective radiators of heat. 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.

Michael Behe further adapted Demski'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)

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. Intelligent design asks whether design can be detected in nature from purely scientific and mathematical considerations. It then attempts to answer that question in the affirmative.

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

Peer reviewed ID publications

Many books on ID have been written but very few ID research papers or monographs have been published in peer-reviewed scientific journals. Many prominent proponents of ID are qualified, practising scientists and it is a weakness of the theory that so little has appeared in the journal literature. This leads some proponents of the theory to suppose that there is some conspiracy or other effort to supress intelligent design discussion in an academic environment.

On 4 August 2004, an article by Stephen Meyer, an intelligent design proponent, appeared in the peer-reviewed Proceedings of the Biological Society of Washington, questioning conventional evolutionary explanations for the Cambrian Explosion and proposing intelligent design as an alternative. Later, however, the Council of the Biological Society of Washington retracted the article. The managing editor for the journal at the time, the process structuralist Richard Sternberg, stated that the article had been properly peer reviewed by three well qualified referees. His decision to publish the paper nevertheless resulted in protests, and colleagues at the Smithsonian Institute, where he was employed, sought to discredit him and created what the The U.S. Office of Special Council (which is authorized to investigate allegations of prohibited personnel practices and activities prohibited by civil service law) called "a hostile working environment".

Criticisms of intelligent design

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.

The view of opponents in the scientific community is 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.

Both philosophical and scientific proponents of intelligent design argue that it is a scientific theory rather than a matter of religious belief, but many members of the scientific community reject this assertion. Opponents of intelligent design who are scientists consider that all of the evidence of complexity in biological systems is open to alternative explanation based on conventional biological theory. There are also very 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 the sense 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.

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, a proponent of intelligent design, 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 eolution, 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. [1]
• Intelligent design movement