Intelligent design (ID) has been proposed as an alternative or a modification to the theory of evolution. The (sometimes unspoken) reason for opposing evolution is that it is seen to be a denial of the religious doctrine that the earth and all living species were created by a supernatural entity. If ID were to be substantiated as a theory, would it provide a possible justification for the existence of the supernatural?
Evolution is a scientific explanation of how there came to be so many different forms of life on Earth. It also explains how there came to be similarities between different types of life form, and differences between individuals of a particular type. Evolution attributes all these differences and similarities to natural processes. It supports and is supported by, but should be distinguished from, those sciences that describe details and processes of known life forms, relationships between life forms, and the time sequences of living and extinct forms.
ID proposes that an intentional process of design is, or was, necessary to produce some or all forms of life. Its proponents claim that many features of organisms could not have arisen as described by evolutionary theory, or, in their words, are “too complex to have happened by chance”. Commonly quoted examples of such complexity are human beings and such organs as the eye. Many scientists have criticised the idea of intelligent design. They claim that it is unscientific, and point to its religious origins.
While the motivation for advocating ID may generally be religious, someone can be persuaded that ID is more likely than evolution by considerations other than religion. A feeling that “there must be a reason behind everything” combined with wonderment at some aspects of nature may be enough. But many committed Christians accept evolution and reject ID.
Some proponents of ID accuse supporters of evolution of being constrained in their thinking and guilty of scientism, that is, of having a blind faith in the truth of science. While the usual view is that science is always subject to correction, however well it may fit all that has been discovered about the world, some scientists and others do have blind faith in its truth, including the theory of evolution.
But scientific theories should not be judged on the behaviour, beliefs or motives of their proponents but on whether they stand up to rigorous query.
Because it has been raised as an alternative to, or, perhaps, a component of, evolution, ID deserves impartial examination as to whether it is a credible scientific theory.
Theory is one of the two components of science, the other being observation – that is, observation of any and all aspects of the world. To be accepted, observations (which often include measurements) should be continually and rigorously confirmed by independent observers, using, where possible, independent methods of observation. We usually then think of them as scientific facts. (But we must still acknowledge that there might be some error in the interpretation of the observations or measurements that has not been noticed.)
Theory is the explanation that logically links all observed facts. There have always been observations for which no completely consistent logical explanation could be found, and theoretical scientists continually “think outside the box” in search of new explanations, which must then be tested. Proponents of ID say they are doing just that. I will later look at ID as a theory, including the implications of its basic concept and what it might explain better than evolution can. But first I will first sketch out some relevant aspects of evolutionary theory.
Evolutionary Explanation of the Development of Species
The basic concept in evolution is that when organisms reproduce, the offspring are similar to but often slightly different from their parents. Occasionally the differences give the offspring some survival and reproductive advantage, which may lead to gradual predominance of the new form. If, over many generations, advantageous changes accumulate, significantly different life forms develop. This is a continuing natural trial-and-error process that enables species to selectively adapt to their environments, making the most of opportunities in the presence of competitors, predators and parasites, which also have developed in the same process. It is not at all like “a whirlwind in a junkyard assembling a Boeing-747”, as the eminent physicist Fred Hoyle once described evolution.
(The term survival of the fittest does not quite capture the essence of the evolutionary process. It is more a matter of proliferation of the more successful adaptors. But while this latter phrase is a better fit, survival of the fittest is the one that will survive.)
The inheritable differences between parent and offspring are explained by changes (mutations) to the parents’ genetic material, i.e., their DNA. All living organisms are structured and operate in accordance with “recipes” coded into their DNA. Mutations continually occur in DNA because of irregularities in the workings of the cells, caused by exposure to unusual chemical conditions, by the insertion of extraneous DNA, or by exposure to radiation. In most cases the internal controls within the cell correct the change. In most other cases the effect of the change is trivial or harmful. In a few cases the change gives some advantage, at least for the environment that the organism finds itself in.
Many kinds of organisms have bodies that can adapt to their environment, such as building stronger muscles or bones and developing immunities to specific diseases, without change to their DNA. Some organisms adapt to various types of stress, such as malnutrition, by modifying the way their genes are expressed within the cells of particular organs. Some of these changes can be inherited in a few future generations but can be reversed by environmental conditions. These are biological processes and some could be factors in evolution.
Contrary to what some people (including some scientists) think, evolution is not purposefully working towards some objective, such as continuously producing greater intelligence. Evolution may be likened to the course of a river, which is not “seeking the sea” but flowing downhill under the force of gravity and deviating as it encounters obstacles. Also, the path of the river is not haphazard, nor is the path of evolution: both are the necessary response to the surrounding conditions. Evolution can be driven by changes in the local conditions, which may offer new opportunities and new threats, or it may drift towards closer adaptation under continuously stable conditions.
Evolution can be illustrated using the development of a complex organ, the eye. A long series of tiny steps starts with a mutation that produces a blob of tissue that happens to cause a reaction affecting the organism when light falls on it. Each successive step provides additional advantage, such as registering the direction of the light, improving focus, and distinguishing detail, colour and movement, producing the many different types of eyes observed among a wide range of species. These different types of eyes have evolved mostly from different starting points, and have developed in ways that meet the particular needs of each type of organism. In most evolutionary sequences, some part of the organism needs to be able to take advantage of each new change, even if the initial advantage is only very small.
We see evolution operating in some of the species we have unsuccessfully tried to exterminate. We see it in the fossil record, where, despite some remaining undiscovered steps (the “missing links”), scientists can now comprehensively “join the dots”. They continually find further fossil evidence and are able to confirm or correct the fossil picture using analysis of DNA. There have been so many species on Earth and so many evolutionary transitions between them that we could not expect to find every stage in each evolutionary path. Given the tumultuous geological history of Earth and the fragility of the tissue of some types of organism, there will always be missing links. This is not an argument against evolution. But the evidence of sequences of stages of evolution of so many species poses a serious problem for ID.
Richard Dawkins has described evolutionary processes so persuasively in his books, such as The Blind Watchmaker and Climbing Mount Improbable, that they seem to be self-evidently true. But Newtonian mechanics also seems self-evidently true. So might there be a successor to evolution – the biological equivalent of relativity? Such a theory need not discredit evolution, but refine or reorientate it. Could intelligent design be such a theory?
A new scientific theory should be able to predict future discoveries. So, what predictions were made by the theory of evolution? When it was first formally proposed there was little evidence of sequential development of the various species, but it was predicted that new fossils would be found that, together with known fossils, would demonstrate chains of development, and that evidence of the ages of various fossils would support the associated developmental sequence. New fossil finds did indeed do just that. And as new sciences developed, e.g., molecular biology and the various methods of establishing the age of fossils, the genetic relationships and time sequences discovered continued to confirm the predictions and to correct some assumptions about earlier discoveries.
This should not stop any alternative explanation from being considered. But if an alternative is proposed, it should also propose a process that does not contradict observed fact. A competing theory should also show how it overcomes any failings of the established theory. So, what are the failings of the theory of evolution?
Critics point to evolutionary explanations of such things as why in human beings the life span is much longer than the period of reproductive ability (in contrast to other species) or how people came to have lost their body hair, or how they began to walk on two feet. These explanations are speculative stories that often sound plausible and may or may not be correct. Some might be shown to have parallels in computer models. But they are usually incapable of being tested or of leading to testable predictions. Often they are countered by alternative speculations that also invoke evolution. Sometimes they may be useful in investigation or therapy.
On the other hand, critics say that evolution must be wrong because, with its connotations of fierce competitive struggle for survival, it is unable to account, for example, for altruism and compassion, which are unquestionable aspects of human behaviour. A plausible (but not necessarily valid) reply may be that there is evidence of these traits among not only humans but in any species that relies on cooperation and some degree of care for the young, so they are obviously traits that can favour continuation of the particular species. Cooperation is found even among bacteria. Computer simulations of interactions between groups of players in which some groups act cooperatively and give help without expectation of reward, and other groups behave competitively all the time, demonstrate that there is survival value in cooperation and altruism. Game theory, which looks at competitive situations from a theoretical point of view, comes to a similar conclusion. Even if this does not seem convincing, the argument about cooperation and compassion is not a refutation of the basic process, described above, on which the theory of evolution is based.
Again, critics point to arguments among biologists and palaeontologists about how evolutionary processes best fit specific observations, and about general principles such as “group” or “individual” evolution, and necessity versus opportunity. These arguments are about biology, palaeontology, etc, and have no bearing on the credibility of evolution as a theory. . Similar kinds of arguments abound in most sciences. The basic description of evolution as described at the beginning of this section accommodates all possible processes of mutation and procreation of inherited characteristics.
Another perceived failing is the purposeless or apparent mechanistic feel of evolution. This offends the intuitive expectations of many people, who consider that life has some supernatural aspect. This is not a scientific objection, and would be hard to defend in any scientific argument. But the evolution of life and consciousness from inanimate matter is something that scientists and philosophers still debate.
Biologists have as yet produced no satisfactory theoretical series of possible steps by which inanimate matter might have developed into living organisms. This is neither a concern nor a refutation of evolution, which is about differentiation of species not the origin of life.
However, the key argument by proponents of ID is that the type of incremental changes proposed by evolution could not possibly produce such complex forms. Biologists, palaeontologists and geologists consider that there is ample evidence to refute this objection, which will be examined in more detail later.
Prevailing theories, including superseded ones, have always had plausible defences against objections. New theories often have a hard time. Two well-known examples from the twentieth century are that continents drift and that Helicobacter pylori is the main cause of stomach ulcers. Both subsequently prevailed: they convincingly addressed the evidence and solved niggling problems. So what about ID?
Implications of a Designer
Intelligent Design as a Scientific Process
ID proposes that desired new forms of life have been intentionally brought into being. No observed natural process or condition supports this, so production of new evidence and a proposed description of the ID process are needed for ID to be justified. No actual evidence or process has been proposed or predicted – at least in the peer-reviewed scientific journals – so I will suggest what a serious theory would need to propose.
It seems reasonable to expect a theory of ID to include conceptualisation, detailed design and assembly. The design might be expressed into the genetic code (which would require comprehensive and precise knowledge of the function and activation of such a code). The designed organism would then be assembled using materials in a “construction factory”, perhaps by inserting the associated codes into a cell as is now done in genetic engineering or cloning. But what type of cell, and how would it be produced and nurtured to adulthood?
Alternatively, entire adults might be assembled, but, if so, how?
And what, specifically, is designed: each species separately, or just some key beginnings and processes? If the latter, it seems very close to evolution, as some ID proponents think. In all cases, the theory needs to propose processes, showing how each design becomes a living organism, how separate species emerge, why there are differences between individual members of each species, how successive generations of a species develop adaptations to environmental conditions and how some members of a species are born with DNA-related diseases. This might imply separate, and sometimes faulty, design of each member of each species, including microorganisms.
Alternatively, the designer might have produced the mutations that evolution attributes to natural causes. But how? And what prompts trivial or harmful mutations? And what about the natural causes of mutations that have already been identified?
Clarifications and proposed processes for these and any other issues would need to be compatible with the consistently observed biological and physical processes and/or to predict the discovery of new processes.
The evolutionary explanation for the production of each new organism is, as described earlier in this chapter, the one we are all aware of: the natural process whereby new organisms develop from eggs produced in the body of the mother. The egg contains the instructions for producing the new organism. The evidence for this is everywhere that organisms reproduce. (For unicellular organisms the process is that the “parent” splits into two new organisms.)
There is a pseudo-scientific claim in support of ID that if an organism has a greater information content than that of the sum of its individual parts, then it must be the product of design. No justification is supplied for this, and there is no reason to suppose it may be true. No evidence has been reported about any measurements of information content of an organ or organism, with a comparison with that of the parts.
A theory of ID would not be complete or sufficient without proposing relevant attributes of the designer. It would need to describe what prompts or compels the designer to make and implement a design, how the designer determines the details of each specific design, and how the designer knows about and interacts with what we call the material world. If new types of forces and/or entities are needed, they should be described in a way that allows independent checking.
If the designer is part of the cause-and-effect natural (i.e., material) world, the theory should be able to describe or predict relevant observable processes. If the designer is outside the material world, it might still use observable processes, but an account would be necessary of how such interaction would occur.
If the proposed processes of design and implementation are not observable, even indirectly, the existence of the designer would be purely a matter of faith. For thousands of years there has been speculation about what might exist beyond the observable world. No unequivocal answer has been found and there is no apparent way of finding one. No designer that was “too mysterious for human beings to describe” could be part of a scientific theory. So it is important for a scientific theory of ID to propose characteristics of the designer that are compatible with what is observed about organs and organisms, and also with the processes by which the design might be created and implemented.
With no attributes of the designer yet proposed, what can be learnt or suggested by looking at life forms in general? As an arbitrary preliminary attempt, some salient things we observe are:
- a very large number of different life forms (species);
- all species depending on DNA for their form and function;
- some species with organs that are inefficient or damage-prone;
- gradations of development of specialised organs in successive similar species;
- certain types of organs appearing at different periods of time in very different types of species;
- a sequence, over a period of billions of years, of extinctions of large proportions of species, after which quite different forms emerge and gradually change and adapt;
- some species closely adapted to a specific environment and ill-adapted elsewhere;
- many species with a relationship of interdependence with other species of very different kinds;
- species with several, apparently unlikely, stages in their life cycle;
- microorganisms living in rock deep below Earth’s surface;
- a cruel food chain, with most species being the prey of other species and/or the host of parasitic species;
- one species, Homo sapiens, that is apparently intent on destroying or enslaving other species;
- species significantly modified by human intervention through selective use of inherited characteristics.
This list suggests a designer with different perspectives and values from ours.
While we might try to deduce what these may be, the list provides neither refutation nor justification of intelligent design. It suggests apparent flaws in the structure of some species, but we should not assume that an intelligent designer would want perfection – assuming there could be such a thing as a perfect organism. An ecosystem needs each of its member species to have both strengths and weaknesses, and some possibility of adapting to changes in its environment.
From this list and, dubiously, using human criteria, some possible conclusions could be that the designer:
- uses only one foundation (DNA) but is very versatile within it;
- is not trying or able to produce trouble-free designs;
- is not solicitous of the welfare of designed forms;
- may be experimenting;
- may have objectives not apparent to us.
Or there may be more than one designer and they are playing some competitive game, reminiscent of science fiction stories or computer games. The mass extinctions that have occurred might have been the ends of games, with new games starting with new species. However, since the extinctions seemed to have been caused by geological events or impacts from outer space and not by contests between groups of species, this is an unlikely story.
All this is pure speculation, suggesting how something might be gleaned, or postulated, about a designer. But there does not seem to be anything in nature that might reveal the attributes mentioned earlier that a designer would need.
It is noted, however, that all this extremely complex sequence of life is occurring in one miniscule portion of the universe. Are there other designers elsewhere, and are they similar to ours, and doing similar things? Some proponents of ID regard the existence of human beings as the objective of a long series of interventions into the natural world by one designer. The interventions begin with the design of the universe with characteristics allowing it to be able to survive and to support life. They continue by making the conditions on Earth just right for humanity. This is a version of what is known as the anthropic principle. It is based on accepted scientific theories that if the components of universe were only slightly different the universe would not have continued to exist, at least in its present form, and if the solar system and Earth were only slightly different there could be no life forms as large and complex as us. (The anthropic principle was discussed in greater detail in Chapter 3 Monism and Dualism: A case for the existence of the supernatural.)
The anthropic argument is just another example of complex coincidences being put forward as proof of a supernatural entity. This matter of complexity and chance is the only serious postulated argument against the theory of evolution. It will now be examined.
Too Complex to Have Happened by Chance
The idea that evolution is “too complex to have happened by chance” raises three questions:
- what does complex mean?
- how complex is too complex?
- what does chance mean?
The word complex, like the word difficult, implies some relationship to human ability. Puzzles are difficult or complex when you don’t know the method of solution, but simple when you do.
Chaos theory has shown that many processes that seemed to behave in a very complex way can be described by a fairly simple equation. Cellular automata –simulations of continued generations of “reproduction”, either computerised or with pencil and paper – demonstrate that complex forms can arise from simple beginnings, using a few simple rules to decide on the survival of members of the present generation and production of new members of the next.
A fishing line can easily get into a very complex-looking tangle that takes a lot of unravelling. Fishing lines and mathematical figures are, of course, much simpler and contain far fewer components than living organisms. But they can come together into ever larger combinations by obeying just a few rules of nature.
Something may look complex when it has a lot of components. But as each one is examined and the interrelationships are understood, the whole may be explained. Many molecules, such as proteins, have a very complex shape because the various forces acting within their component atoms push them into tangled contortions. The laws of nature produce complex forms everywhere, in ways that are explicable, even though the explanation might require many steps.
A rough way of comparing complexities would be to compare the number of parts. A refinement would be to compare the number of different kinds of parts, and then the number of relationships and types of relationships between the parts. But when we marvel at living complexity, it is usually not the statistics that impress us but that the particular organ or organism is structured to perform so well.
A puzzle may be too complex for a four-year-old child but not for a ten-year-old, because spatial, numerical and other concepts develop as a child matures. A problem may be too complex to resolve without certain information. Many mathematical problems that were too complex to calculate without a computer have been solved using one.
There are mathematical problems that get disproportionally more difficult as the number of components increases. One well-known example is the travelling salesman problem. The salesman has to visit several places that are scattered about in no particular order. The problem is to find the shortest overall distance the salesman must travel in visiting all the destinations. With only four destinations the problem is easily solved, but it quickly becomes much more difficult as the number of destinations increases. Irrespective of the number of destinations they have, real-life salesmen manage to get to all their customers, even though they may not have taken the shortest route. Evolution is a process that happens in the physical world, and, like the route of the travelling salesmen, the adaptations it provides are not necessarily the best that might have been possible.
There are much more difficult complex mathematical problems than that of the travelling salesman, and some of them also relate to actual circumstances. So what circumstances make evolution of species impossibly complex?
Proponents of ID make various claims. Some say that most organs and organisms could not be functional if certain significant parts were removed. They call this “irreducible complexity”. Of course no organ or organism can function if vital parts are removed, but this does not mean that ancestors of existing species could not have had simpler or rudimentary versions. So proponents of ID also claim that certain organs could not function in any form simpler than what now exists.
However, the structures of biological organs are continually being investigated, categorised and recorded, and their operations are continually being better understood. They generally, and specifically the ones referred to as being irreducibly complex, are found to have simpler counterparts in present or extinct species. And what of the very first ones? They appear to have come from simple chance mutations that incidentally brought new types of capabilities, as in the description, given earlier, of the development of eyes.
A similar claim is that, since all components of complex structures specifically complement each other, they must have been designed together. The evidence shows that biological components sometimes develop in step with each other, and sometimes a mutation may incidentally provide a new use for some particular part of the body.
An improved model of a designed artefact, for example, a motor vehicle, may incorporate a dramatically new version of any of its parts or a major rearrangement. In an evolutionary process such types of change are impossible, because no radical change to an organ could survive unless the rest of the system was rearranged at the same time to fit it. Therefore many organs with inherently inefficient or damage-prone features persist over long periods of time and across a range of similar species. This shows that these particular structures are stuck in an evolutionary rut rather than being the result of (faulty) design. One example is in the eyes of mammals, including human, where the nerves carrying the signals from the retina to the brain are in front of the retina, partly blocking it from what it is viewing. Some unrelated species, such as cuttlefish, have eyes somewhat similar to mammalian eyes but which developed separately without this apparent flaw, i.e., the nerves are behind the retina. (Mammalian brains have evolved so as to render unnoticeable what would otherwise be a blank in their vision.) There are many other examples of evolutionary ruts.
But, accepting that some adaptations might have occurred through natural processes, could all the modifications required by evolution have really occurred by chance? To answer this we should examine the concept of chance.
To say something happened by chance means that either it was unexpected or we can’t tell precisely what caused it. The history of science and technology is replete with discoveries that occurred because something “went wrong”, i.e., happened (unexpectedly) by chance. Similarly, chance occurrences bring significant people together in all fields of life, including science, and continually affect the course of history.
Many significant things in most people’s lives happen by chance: their first meeting with their future life partner; the way they started in their “chosen” profession; or how they were the unlucky victim of some accident. Almost everyone remembers a few trivial coincidences in their life but forgets most of them. Coincidences happen in great profusion, just through sheer chance..
Chance implies not only uncertainty but also probability. Often the probability of a particular event occurring under certain circumstances can be calculated. Complete certainty is expressed as a probability of 1 (one). Being just as likely to happen as not happen (“a fifty-fifty chance”) is a probability of 0.5. And no chance whatever is a probability of 0 (zero). But the nature of chance is that, even though the probability of something may be high, it might not happen if there are only a few occasions where it could happen. And when the probability is low it might still happen on the first or second possible occasion.
We often have intuitive ideas about the probabilities of unusual occurrences, but we frequently get it quite wrong. For example, if a group of people gather together (for reasons that have nothing to do with birthdays) how many people would need to be present for a fifty-fifty chance that there will be at least one pair with the same birthday? Given that there would need to be 367 people for complete certainty of one such pair (because of the possibility of 29th of February birthdays) and two people for the minimum possibility, something like about ninety people might feel reasonable for a fifty-fifty chance. But mathematical calculation and repeated trials both show that only twenty-four are needed. Understanding the conditions and processes can show how pure-chance coincidences that seem very unlikely may really be very probable. If there is some sort of bias in a process, such as in rolling loaded dice, certain outcomes will be more likely than with true dice. In the process of evolution there is the bias of natural selection, which leads to certain coincidences being more likely than if no individuals had any reproductive advantage. Also, once a chance mutation occurs in a genome there is a strong bias towards it being transferred to at least a few succeeding generations. Calculating probability on the assumption of the wrong process or conditions can lead to wildly incorrect results.
Proponents of ID, who talk of “specified complexity”, alleging a very high improbability of evolution, do not understand this. Their improbabilities relate to a process where all the components of a particular organ or organism somehow come together to complete a pre-designed arrangement in one single step – like the whirlwind in the junkyard. This is the antithesis of evolution, in which, at each of an enormous number of steps, the actual outcome was just one of many potential alternatives. Evolution is not the outcome of some pre-designed process of producing a particular kind of organism. It is the continual production of generations of different kinds of organisms, in which the individual members of almost every kind of organism are all different in some way from each other and from members of the previous generations. The outcome of every step for every kind of organism always includes an element of chance.
With large numbers of organisms continually taking in and converting food and energy in a changing and chemically reactive environment, very many significant interactions keep occurring, inducing inheritable mutations in very many individuals. Continual mutations to DNA make it very probable that some members of succeeding generations will continue to survive or prosper whenever their environments change. Or the mutations may allow some members to produce more offspring than other members in a stable environment, or enable some members to take advantage of aspects of their environment which their fellows are unable to. (Many mutations will, of course, be harmful. These mutations will die out. Others will have little or no effect. But the comparatively few that confer advantages will drive evolution.)
Similar kinds of natural mutation have enabled people to breed different strains of plants and animals. For example, dog-breeders have selected for size and structure of the body, structure of the retina, innate inclination and ability to round up sheep or retrieve game, etc., to produce dogs that excel at specific tasks. This demonstrates “survival of the most appropriate”.
The great range of environments on Earth, changing from place to place and from time to time, continually provides opportunities for the diversifications to develop into new species. The prolific progeny of most species, each having to struggle to reach maturity, amplifies this process. Chance, therefore, makes evolution eminently feasible.
This doesn’t mean that speciation must have occurred through natural processes, but it discredits the argument that evolution is statistically unlikely. Indeed, to attempt to calculate the probability of anything that happened to have developed in such prolonged, complex and unknowable circumstances would be futile.
(Because chance is an essential aspect of evolution, I think the term natural selection is a misleading misnomer. The word selection implies choice and some purpose for making the choice. There is no purpose or objective in evolution. There is just chance. And the outcome depends on the particular conditions at each particular event. Nevertheless, many people think evolution has a direction – towards greater complexity, greater capability and greater intelligence. This starts to look like design.
Richard Dawkins, in his book Climbing Mount Improbable, points out that it is not only structures that reach evolutionary ruts, it is also species. An evolutionary rut is a condition where no possible mutation will provide any evolutionary advantage. In such cases the particular species may be sidelined, or replaced by another species with a different ancestry or just become extinct. In the case of human intelligence, it might be argued that it is already making us powerful enough to destroy ourselves along with many other species, given that our emotions often make us act without due thought of the consequences. Perhaps, as some people think, our emotions and/or our society will evolve in a way that would prevent this. Perhaps not – it will be just a matter of chance.
In any case, if there is to be a last survivor of life on Earth, it is much more likely to be a bacterium than any complex organism.)
Can Intelligent Design Stand Up as a Theory?
In the public debate about ID, much of the heat is the result of peoples’ hopes that a scientific theory will support, or not undermine, their religious, philosophical or political beliefs. But no scientific theory – evolution, ID or anything else – should ever be considered as the final word. A theory is merely a tool – for explaining observations, for guiding and assisting further research and for the development of new technology. Sometimes evidence supporting a new theory is staring us in the face but is not recognised. Occasionally a new entity is discovered, e.g., the nuclear forces during the twentieth century. Many scientific riddles await solution at this moment. But no new theory will be accepted as “correct” unless it is useful or reflects the evidence more logically than any other.
There seems to be no existing observation of nature that would put the theory of evolution in need of any replacement or revision, e.g., the discovery of organisms that could not have resulted from evolution. Examples might be ones similar in most respects to existing species but with some organs radically different – like cats with non-mammalian eyes – or whose form and processes depended on something very different from DNA. No such evidence has yet been found.
This discussion has put both ID and evolution on trial, but it is an uneven situation. A refutation of ID would merely affirm the standing of evolution, which is supported by extensive evidence. But a refutation or weakening of evolution would not yet mean that ID must be true, or even plausible, because of the weakness of the current claims in its favour.
At this stage, ID is an incompletely developed reaction to the theory of evolution. Its concept introduces an entity and types of processes that are unknown to science. To be a scientific theory it would need to propose testable processes that logically explain the diversity between and within species. It would also need to propose the characteristics of a designer compatible with those processes, and to demonstrate cases of the designer performing the processes. None appear to have been offered.
That is not to say that it would be impossible to develop a successful rigorous theory around the idea of intelligent design, but the difficulties introduced by the concept seem insurmountable. But even if such a theory were developed, it would not supersede evolution unless it could logically explain everything that evolution explains, and also something that evolution cannot explain. And with such a theory, the hypothetical designer need not be supernatural.