Intelligent Design: Is it scientific? (is there evidence? proof?)

This page is an introductory overview.
Most of it was originally in The Origin of Life:
3. Closed Science and Open Science
4. What is a theory of Intelligent Design?
5. Can a theory of intelligent design be scientific?
6. Origin of Life? The Science of Chemical Evolution
7. Can design be proved? What about future science?
8. Scientific Evaluation plus Philosophical Interpretation

Appendix: complexity csi 100% no-yes abilities stardust virtues

Some sections (3, 4, 6, 7) are condensed — they contain excerpts from the original page, to quickly show you the main ideas — while others (5, 8) are more complete. Two related pages, with "the rest of the excerpts," are Four Types of Intelligent Design and Methodological Naturalism: Science, Philosophy, and Theology.

3. Closed Science and Open Science

Currently, most scientific inquiry is closed by methodological naturalism (MN), a proposal to restrict the freedom of scientists by requiring that they include only natural causes in their scientific theories. In a closed science (restricted by MN), evidence and logic are not the determining factors because the inevitable conclusion — no matter what is being studied, or what is the evidence — must be that "it happened by natural process."

Is MN the best way to do science? Maybe not. It depends on what actually happened in history. ..... [much of the original section has been omitted]
If we don't know whether history has been all-natural, our best scientific strategy for finding truth is an open science, with scientists humbly asking a question instead of arrogantly assuming an answer.
In open science a scientist begins with MN by assuming that "it happened by natural process." But an open-thinking scientist is free to use both MN and non-MN modes of thinking while logically evaluating the evidence, to consider a wider range of possibilities. A scientist begins with an MN-assumption, but does not insist that — no matter what the evidence indicates — it is necessary to end with an MN-conclusion. An open scientist adopts testable-MN instead of rigid-MN, because the assumption of MN is treated as an assumption, as a theory to be tested rather than a conclusion to be accepted. There is flexible open-minded inquiry, with freedom of thought for the individual and community, and scientists are free to follow the evidence-and-logic wherever it leads. Each theory is evaluated based on its merit, and if a non-MN conclusion is justified by the evidence, this is allowed. ..... By contrast,

The Conclusions of MN-Science — that no matter what is being studied, or what is the evidence, it happened by natural process — are actually The Assumption of MN. The circular logic of MN, which converts a naturalistic assumption into a naturalistic conclusion, is illogical (because circular logic is bad logic) yet is unavoidable, and it requires no science. But instead of acknowledging this logical weakness of MN-Science, usually MN-Humility is ignored and there is an implication that the assumption made by MN (that it happened by natural process) is a conclusion reached by science, and is therefore true. MN provides a way to bypass the process of science and then claim the authority of science as support.

MN is examined more thoroughly in a page about Methodological Naturalism that contains all of Section 3, plus excerpts from three other pages.

4. What is a theory of intelligent design?

If you receive a radio signal — 2, 3, 5, 7, 11, 13, 17,... — and you think "this long string of prime numbers was probably not produced by undirected natural process," you are proposing a theory of Intelligent Design.

< snip: part of the full section — which you can read in Four Types of Intelligent Design — is omitted here >

All theories of divine creation propose intelligent design, but usually a "Design theory" has a narrower definition, as explained in the conclusion of the full section:

When you're reading the rest of this section, you may wonder "why is he making it so complicated by distinguishing between four types of design, and between Design (specific with a narrow definition) and design (general with a broad definition)?" My answer is that these distinctions are important and are necessary, because without them our thinking can be illogical and our communicating can be confused. Einstein said "we should make things as simple as possible, but no simpler," and making it "as simple as possible" requires these distinctions. If you read carefully while thinking, you'll see that this system of terms (with four types of design, which include two types of Design) is necessary and it does make sense; this system will be useful because it will improve our thinking and communicating, helping us think more logically and communicate more clearly.

Design (specific, narrowly defined) and design (general, broadly defined)
For improved precision, I'll use words that are Capitalized and regular to distinguish between Intelligent Design (defined narrowly) and intelligent design (defined broadly).
In this page, and in most other contexts, a Design theory is a claim that a feature was produced by empirically detectable Design-directed action during history (by Dn-or-Ds, with Design-action by a natural agent or supernatural agent) rather than Ni (design of nature, which is not during history), Ns (design-directed guidance of natural process, which is not empirically detectable), or Nu (which is not by design-directed action).
My definition of design is broader; it includes Ds-or-Dn (Design) and also Ni and Ns (which are not Design but are design). Therefore, of the five possibilities — Natural-initial design (Ni), Natural-supernatural design (Ns), Detectable-supernatural Design (Ds), Detectable-natural Design (Dn), and Natural-undesigned (Nu) — four are design and only one (Nu) is non-design.

The table below shows the four types of design (in the three columns with a white YES) and the three questions that are used to define design (Does the production of a feature involve design-directed action?) and Design (Does the Design-action occur during history and is it empirically detectable?).

Dn. Design-action by natural agent
Ds. Design-action by supernatural agent

Ni. design of natural process
Ns. guiding-action for natural process
Nu. natural process that is undesigned
and (in history) is unguided/undirected

design and Design defined in terms of three questions	design
	Design	non-Design
	Dn or Ds	Ns	Ni	Nu
design-directed action?	YES	YES	YES	no
occurs during history?	YES	YES	no	—
empirically detectable?	YES	no	?	—

testing for Design and design: Using my definitions, a feature was produced by either Design (Dn-or-Ds) or non-Design (Ni, Ns, or Nu), so Design and non-Design are mutually exclusive, and evidence for one is evidence against the other. But design includes Design and more, so evidence against Design (during history and detectable, Dn-or-Ds) is not evidence against the other two types of design, by design before history (Ni) or undetectable design-action (Ns).

note: This system of terms — distinguishing between Design (specific, narrowly defined) and design (general, broadly defined) — is my own system. Other authors have not used it in the past, and probably most will not use it in the future, although I hope the ideas in it will be considered and accepted. The full page about "four types of design" uses the system's two terms consistently, but in this page (and in almost all other pages you'll be reading, by me and by other authors) "design" can refer to either Design or design, and you'll have to think about the context and decide the intended meaning.

5. Can a theory of intelligent design be scientific?

Design is Testable in Science
Design can be tested using scientific logic. How? When we use the definitions above, design and non-design are mutually exclusive (it was one or the other) so we can use eliminative logic: if non-design is highly improbable, then design is highly probable. Thus, evidence against non-design (against production of a feature by undirected natural process) is evidence for design. And vice versa. { the logic of mutual exclusion and questions about defining design-action } The evaluative status of non-design (and thus design) can be decreased or increased by observable empirical evidence, so a theory of design is empirically responsive and is testable. Based on a logical evaluation of evidence, we can conclude that a design theory is probably true (if all non-design theories seem highly implausible) or is probably false (if any non-design theory seems highly plausible). { But can design be proved? What about future developments in science? }

Observable Signs of Design
How do scientists detect design? By using eliminative logic, as explained above. This logic can also be described in terms of the characteristics (including complex specified information) that typically are produced by design-directed action, but not by undirected natural process. Scientists have developed, and are continuing to develop, ways to recognize these signs of design, which seem to occur only when a design-idea has been actualized by design-action.
If we observe strong signs of design — such as a long string of prime numbers, or circumstantial evidence for a murder — we can infer that design-directed action did occur, even if the agent and action were not observed. Scientists can infer the existence of an unobservable cause (an electron, a thought, a volcano acting in the past, a person acting in the past,...) from the observable effects it produces, in studies of current events or historical events, with or without agent-action.

Can historical science be scientific?
The scientific methods used in a design investigation are also used in historical sciences like geology, archaeology, evolutionary biology, and astronomy. Many arguments against design are also arguments against every historical science. But scientists have developed methods for coping with the limitations of historical data, and historical science can be authentically scientific. The same principles of scientific logic are used in both operations science (to study the current operation of nature, what is happening now) and historical science (to study the previous operation of nature, what happened in the past). { Historical Science — Do evolution and design use scientific method? }
A historical theory can include proposals for agent-action in history. In some historical situations, only undirected natural process was involved, so a mechanistic explanatory theory (which usually is related to mechanistic theories in operations science) is adequate. In other historical situations, what happened was affected by the decisions and actions of an agent. This introduces an element of unpredictability when making predictions, but this is acceptable because in a descriptive theory a historical scientist (in anthropology, archaeology, history, sociology, psychology, or forensics; or in geology, biology, paleontology, or astronomy) only has to determine what did occur, not predict what will occur. And in an agency explanatory theory, proposing that "agent action was involved" is part of the scientific explanation.

Details about Design (are not necessary)
For any question about design, in any area (radioastronomy, homicide, origins,...), we can view the scientific inquiry as a two-stage process: first we ask "Was there design-directed action?", and then we investigate the details. A basic design theory claims only that design-directed action did occur (the first stage) but does not try to explain the details (who, why, how,...) of design-and-production.
Of course, we should evaluate a design theory based on what it does claim (that design occurred) instead of what it does not claim (that it can explain the details). { An objection claiming that a basic design theory is not sufficient. }

Design is Common in Science
In science, theories of design are common. In every design investigation, scientists ask the same question: If we assume a uniformity of natural process, was undirected natural process sufficient to produce what we observe? Sometimes the answer is "probably not," and design-action is proposed to explain a wide variety of features such as bird nests, ant hills, predator-prey events, paintings on a cave wall, metal satellites in orbit, and faces on Mount Rushmore. A design theory is proposed — for example, when a crime detective concludes that "this death occurred by murder, not natural causes" — when an inference that "design-directed action did occur" can be justified based on a logical evaluation of evidence.
Design is common in science, and most design theories (but not all) are judged on their scientific merit. Why is there a difference? The main reason, as explained in Four Types of Design (and why one type is controversial), is that "concerns about design occur when design-action seems unfamiliar... and it could be supernatural. In these situations the main concerns are religious, and a common claim is that a design theory is a creation theory." But even though "the main concerns are religious" there are also logical reasons for caution when we ask "what are the goals of science, and what methods should be used to pursue these goals?" These questions — about goals and methods — deserve more attention, and I will discuss them in more detail later. Currently, the appendix includes more about methods for detecting design by using the logic of mutual exclusion, along with interesting questions (about divine guidance, intelligence & detection, goals & abilities) and some useful ways to think about these questions.

What difference will it make?
Although design might significantly affect philosophy of science, probably it will have little impact on the overall productivity of science, because most areas of science are not affected by controversial claims for design. But in several historical areas — including origins of the universe, first life, and complex life — scientific analysis shows that design deserves to be accepted, not as the only possible explanation, but as a potentially plausible explanation that is worthy of serious consideration and further development. The potential of design theories to make valuable scientific contributions should be recognized and welcomed.

Will it be scientifically productive? ( Is it a science-stopper? )
Perhaps the search by Closed Science (restricted by a rigid methodological naturalism) is occasionally futile, like trying to explain how the faces on Mt Rushmore were produced by undirected natural processes such as erosion. If scientists are restricted by an assumption that is wrong (that does not correspond with historical reality) the finest creativity and logic will fail to find the true origin of the faces.
Occasionally, perhaps MN is forcing scientists into a futile search, like a man who is diligently looking for missing keys in the kitchen when the keys are sitting on a table on the front porch. No matter how hard he searches the kitchen, he won't find the keys because they aren't there! On the other hand, if the keys really are in the kitchen, they probably will be found by someone who believes "the keys are in the kitchen" and is diligently searching there, not by a skeptic.
Perseverance and Flexibility: How is scientific productivity affected by attitude? In the complex blend that generates productive thinking, "There can be a tension between contrasting virtues, such as persevering by tenacious hard work, or flexibly deciding to explore new theories that may be more productive in a search for truth. A problem solver may need to dig deeper, so perseverance is needed; but sometimes the key to a solution is to dig in a new location, and flexibility will pay off." {from Productive Thinking: Creative and Critical }

If you get stuck while trying to solve a problem, you must decide whether to continue in the direction you're going or change course.
Sometimes PERSEVERANCE is needed, and you should DIG DEEPER:		But sometimes FLEXIBILITY is needed, so you should DIG ELSEWHERE:

Should scientists dig deeper in the same location, or dig in a new location? Should they search the kitchen or porch? The answer is YES if we notice that one word is wrong, if we replace "or" with "and" because we refuse to remain trapped in narrow thinking. Instead of thinking that we must make an either-or choice, we should search both kitchen and porch, we should dig deeper and in new locations, as suggested in open science. We can adopt a humble attitude "by refusing to decide that we already know with certainty... what kind of world we live in." { more about the paradoxical virtues of flexibility and perseverance }
One night you find a man searching under a streetlight. You ask why, and he says "I'm looking for my keys." You ask, "Did they fall out of your pocket?" "Yes, I was riding my bike when I heard them hit the ground about a half-block up the street." "Then why are you searching here?" "It's easier to search here because there is more light." / Why is this a joke? Is he behaving rationally? Will he find the lost keys?

But if scientists accept a theory that "a designer did it," what else is there to do? Therefore, isn't a claim for design a science-stopper?
No, this simplistic "slippery slope" argument is hindered by the inflexibility of narrow either-or thinking. It is unrealistic because when most scientists hear a claim that "maybe a non-design explanation doesn't exist" they will continue their non-design research, probably with renewed vigor because they are responding to a challenge.
Currently, some scientists think "design-directed action" is the best explanation for some features, such as the origins of the first life or of some biocomplexities. Other scientists don't "accept" design, but they think that, for some features, a theory of design-action should be seriously considered. But currently most biologists (including those who are open-minded about design, and those who aren't) still think non-design is the best explanation for all features, and they certainly expect non-design research to be more scientifically productive for generating useful information and for explaining a wide variety of features in organisms and in their historical development.
I agree. Compared with design theories, I think non-design theories (especially the modern synthesis of neo-Darwinism) will continue to be much more scientifically fruitful in stimulating research that will help us learn more about the history of biological development on earth. But even though this research activity is stimulated by non-design, it could either increase or decrease the status of non-design theories, as explained in Section 7. But design theories could also be useful in stimulating scientific research and thinking (this is discussed in DESIGN IN SCIENCE), especially when the perspectives of design and non-design are used together in a flexible combination.
Proponents of design want non-design research to continue so we can learn more, so we can more accurately evaluate the merits of non-design and design, because the goal is to find truth. They want to supplement non-design research, not replace it. They want to stimulate productive action and critical thinking, with invigorating debates between critics of a theory and its loyal defenders. This type of scientific stimulation did occur (and is occurring) due to Michael Behe's claims for "irreducible complexity" in 1996, even though (as explained in Mike Behe's Adventures with Science Journals) the current scientific community does not want to acknowledge or encourage this scientific stimulation.

The main part of this page ends by looking at current science (6), future science (7), and philosophical evaluations (8).

6. The Science of Chemical Evolution (Part 2)
In the full-legth page, this section explains why "scientists are learning that the complexity required for life (in terms of biomolecule formation and self-organization) seems to be much greater than the complexity available by natural process (beginning with lifeless matter). This huge difference has motivated scientists to creatively construct new theories for reducing requirements and enhancing possibilities, but none of these ideas has progressed from speculation to plausibility. ....." {more about origin-of-life science}
It also describes the concepts of irreducible complexity (developed by Michael Behe) and "the minimal complexity that would be required for reproduction and other essential life-functions" in the first living organism. {two complexities of life}

7. Can design be proved? (excerpts)

As explained in Section 5, a design theory is "empirically responsive and testable" because "design and non-design are mutually exclusive." But a design theory does not claim non-design is impossible and design is certain, it only claims that design seems more probable based on scientific evidence and logic. {one reason we cannot be certain} This type of probability-based conclusion is consistent with the logic of science in which proof is always impossible, even though scientists can develop a logically justified confidence in the truth or falsity of a theory. ...
All current theories for a natural origin of carbon-based life seem implausible. Is it rational for scientists to consider the possibility that life on earth did not originate by undirected natural process, but was the result of design-directed action? The certainty of "proof" is impossible because we can never propose and test all possibilities for non-design. But we could develop a logically justified confidence that our search has been thorough yet futile, and no promising approaches remain unexplored. ...

What might happen in the future of science?
Even though advocates of non-design imply that future science will support their claims, the change in support could go either way, up or down. Will non-design seem more plausible because we have discovered how a feature could have been produced by undirected natural process? Or will it seem less plausible because we have learned more about the limits of natural process? Either of these results could occur. In fact, both changes have occurred in the history of research about chemical evolution. ... Compared with fifty years ago, now we know more about the origin of life, and what we've learned has made a natural origin of life seem less plausible. ...
In the future, what will happen in science, and how will this affect the status of non-design and design? When thinking about this, we can use our imaginations to predict improvements in current theories and inventions of new theories. And we can use current knowledge to guide our questions. Most of the skepticism about current theories of chemical evolution is based on what we know, and this knowledge can help us ask specific questions. We can look at each obstacle to a natural origin of life — such as the unfavorable chemical reactions needed for making biomolecules, the high degree of biocomplexity needed for metabolism and reproduction,... — and try to imagine ways in which future knowledge might change our views about each obstacle. We can ask, "How likely is each change?" and "How would it affect our evaluations for a natural origin of life?" {an alchemical example, comparing 1600 and 2000}
To make good predictions about future scientific developments, we need creativity (to imagine what could be) plus criticality (to make realistic predictions about what is probable in reality, not just possible in our imaginations) so we can avoid the extremes of insisting that in this area of science "nothing new will happen" or "anything could happen." ... { This section has been condensed, as indicated by the ...'s, to 1/3 of its original length. }

a useful concept: As in other models of science, my model of Integrated Scientific Method uses a continuum of theory status ranging from very low to very high, to describe our degree of confidence in a theory. This concept encourages flexible thinking, by not limiting us to the dichotomous alternatives of accepting or rejecting a theory. These binary categories are still available — because if status rises above a certain level we can "accept" a theory, and if it falls too low we can choose to "reject" — but a binary choice (either yes or no) is not forced on us prematurely due to rigid concepts that have limited the options we are capable of imagining and considering.

8. Scientific Evaluation and Philosophical Interpretation
In the full version of Section 7, I ask you to "imagine a scientific community with trillions of super-intelligent space aliens [with long lifespans and technology for exploring throughout the universe]... who [after billions of years of their super-science] have not yet constructed a plausible theory for a natural origin of life." And I ask a question: "Even in this situation a denial of design would be possible, but would it be rational?"
This difficult question does not have an easy answer for us, because 1) in the near future, the actual state of human knowledge will remain much less advanced than in the super-science of this imaginary scenario, and 2) a design theory, and any other theory, can be rationally evaluated in two ways, using science and philosophy:
• Scientific Evaluation of a theory: First, we use evidence-and-logic to evaluate each current non-design theory for plausibility, and we use creativity (to imagine what could be) plus criticality (to make realistic predictions about what is probable in reality, not just possible in our imaginations) in an effort to predict improvements in current theories and inventions of new theories.
• Philosophical Evaluation of a theory: Second, based on a wide range of scientific and nonscientific criteria (including worldviews) we think about the possibilities for how a feature was produced: 1w (a natural event of low probability, which did occur even though it is scientifically implausible), 1w* (if events with apparently low probability are actually highly probable because there is an immense number of universes), 1x (a current naturalistic theory is approximately true), 1y (a future naturalistic theory will be approximately true), 1z (a naturalistic theory is true, but we will never propose and accept it), 2A (natural design and construction), or 2B (supernatural design and creation). All of these are logically possible, but — based on our interpretations (which are based on scientific and nonscientific logic, plus personal experience and values) — do we think they are equally probable? {note: These seven possibilities are explained more thoroughly in Section 7 of The Origin of Life: A Test-Case for Naturalism? }
A major challenge in evaluating design is uncertainty about the adequacy of our current science. Although design (2A or 2B) and non-design (1w, 1w*, 1x, 1y, or 1z) are mutually exclusive, our estimates for the status of non-design (with five possibilities!) are uncertain. Advocates of non-design and design disagree about the status for current non-design theories (1x), but their disagreement increases when trying to evaluate the other four possibilities for non-design, which include highly improbable events (1w, 1w*) and deficiencies in current science (1y, 1z).
During our evaluations, we should recognize that proof is always impossible in science. An important aspect of philosophical interpretation is deciding what to conclude (or whether to conclude) when a logical scientific evaluation, based on currently available evidence, is not conclusive.* If a design theory claims only to be "more probable" or to warrant "a high level of confidence," this is the standard by which it should be judged. It seems unreasonable for critics of design to demand — along with radical postmodern critics who challenge the credibility of all science — that if scientists cannot claim the certainty of proof, they can claim nothing. We should want to be appropriately humble by avoiding the extremes of arrogant overconfidence (in claiming too much) or timidly overcautious relativism (in claiming too little) and not descending into aggressive postmodern skepticism about the futility of logic and the illusion of reliable conclusions.

* In baseball, most umpires have decided to use the arbitrary guideline that "a tie goes to the runner." In U.S. courtrooms, the usual rule of "assumed innocent until proved guilty beyond a shadow of doubt" is based on a non-arbitrary principle of freedom. In science, sometimes there is a strong guideline (an "unwritten rule" that is understood by all) based on a principle of protecting the currently reigning paradigm against all challengers. {defending a paradigm} / an application: When we're comparing theories of design and non-design, does design (the challenger) have "the burden of proof" and does non-design (the paradigm, the reigning champion) get "the benefit of the doubt"? (but how much proof is required, how much doubt is allowed?)
In the few areas where design is challenging the status quo, an attitude of "defending our champion against the challenger" may be the way it is now, but is this the most rational way to search for truth? In baseball, a quick decision is required so the game can continue. But in science, instead of "declaring a winner" can we just say "we're not sure at this time" and continue searching, with this humble open-minded attitude, in our efforts to learn more?
It seems rational to adopt different levels of status for different claims about design. Instead of deciding that a binary choice (either YES or NO) is necessary, we can decide that different types of claims for the origin of a particular feature — ranging from bold to humble, claiming that design is almost certain, is highly probable, is more than 50% probable (so design is an "inference to the best explanation"), is moderately probable, or is plausible enough to be seriously considered as a possibility — should be judged to have progressively increasing levels of scientific status.

Should we ask the question?
Design cannot be proved, but in science the goal is logically justified confidence and a high degree of plausibility, not certainty. When we ask, "Was design-action involved in producing this feature?", it will be impossible to answer with certainty. But it should be easy to decide, "Should we ask the question?" A curious, open-minded community will say "YES, we want our science to be flexible and open to inquiry."

Section 8 was motivated by a similar suggestion for "science plus interpretation" by Loren Haarsma in Science and Miracles.

Appropriate humility also seems justifiable in theologies. For example, all Judeo-Christian theists believe that God intelligently designed the universe, but I think there is not a compelling theological reason to believe that God did (or didn't) design the universe to be totally self-assembling by natural process, so theists can be appropriately humble about God's method of creation, and we can look at the scientific evidence-and-logic with an open mind. (*) We can be humble while we explain — using arguments based on theology and science, based on our interpretations of scripture and nature — why we think one view is more plausible than other views. { The ideas in this paragraph are condensed from the conclusion of "Why is it controversial?" in Four Types of Design. } * Can atheists look with an open mind?

APPENDIX

Two Questions about Complexity Complex Specified Information
The Logic of Mutual Exclusion Design? Intelligence & Intention
Can we observe divine guidance? Details about Design (Part 2)
A Backward Look at Future Science Flexibility & Perseverance

Two Questions about Complexity: Irreducible and Minimum (excerpts from Section 6)
In Darwin's Black Box: The Biochemical Challenge to Evolution (1996), Michael Behe illustrates the principle of irreducible complexity with a mousetrap that has five interacting parts: a base, hammer, spring, catch, and holding bar. Each part is necessary, and there is no function unless all parts are present. A trap with only four parts has no practical function. It doesn't just catch mice poorly, it doesn't catch them at all. .....
For a nonliving system, the implications [for a step-by-step process of gradual improvement through natural evolution] are even more challenging, because natural selection — which is the main mechanism of step-by-step Darwinian evolution — cannot exist until a system can reproduce. For the origin of life, we can think about the minimum complexity that would be required for reproduction and other basic life-functions. Most scientists think this would require hundreds of biomolecular parts, not just the five parts in a simple mousetrap.

Complex Specified Information
A prominent design theorist, William Dembski, suggests using the concept of complex specified information when thinking about signs of design. A short string of prime numbers (like "2 3 5") is not complex, so it could easily occur by chance. A long string of random numbers is complex, but is not "specified" because it has no pattern. But a long string of prime numbers is complex and (due to its conceptual functionality) is specified, and it contains functional information. { Soon, I'll link to more thorough explanations of specified complexity: a summary by someone, and a longer page by Dembski. }

Testing for Design (by using the logic of Mutual Exclusion)
When theories of design and non-design are carefully defined they are mutually exclusive. Similarly, DESIGN and non-DESIGN are mutually exclusive. As shown below, two sets of categories — either non-design and design (this set is most important in science) or non-DESIGN and DESIGN (this set is theologically important) — will "cover everything."

Because non-design and design are mutually exclusive, either one or the other must occur, so together their probabilities add to 100 percent. The table below shows the relationship that allows design to be tested by testing for non-design. For example, if the estimated probability of a non-design cause decreases from 30% to 10%, the estimated probability of a design cause increases from 70% to 90%.

%-probability of non-design	100	99.99	90	70	50	30	10	.01	0
%-probability of design	0	.01	10	30	50	70	90	99.99	100
SUM of %-probabilities	100	100	100	100	100	100	100	100	100

The two gray-shaded regions are a reminder that the 100%-certainty of "proof" or "disproof" are impossible in science, and are not the goal in science. As a reminder that the outcome of theory evaluation is an educated estimate rather than a claim for certainty, it can be useful to think about a continuum of theory status, ranging from very low to very high, to describe our degree of confidence in a theory.

The three sections below illustrate some of the complex subtleties that occur when we think about design:

Can we observe a guiding of natural process? (no and yes)
A directing of natural process can be detected, in principle and usually in practice, IF the observational data is adequate and our logic is skillful. But for various reasons, sometimes an agent wants design-action to be undetectable, as with the design-directed action of an illusionist (entertainment magician) who "directs" things in a way that is difficult to detect, or a criminal, plastic surgeon, or in the special effects of a movie-maker, or when God "guides" natural process. Why isn't God more obvious?
One possible type of intelligent design is achieved by a divine guidance of natural process. I define natural as "normal appearing" so (by definition) the guiding of a natural-appearing event cannot be detected. But...
Sometimes a series of undetectable events can become detectable, as in this example: If you pick the winning number for a roulette wheel once, it looks natural. But what if the wheel is guided by God so you win 20 times in a row? Each event appears natural, but the overall process (with 20 events) does not appear to be undirected natural process, and most observers will think "the wheel was rigged."
Perhaps some biological complexity was created when God combined many individually undetectable "guided natural events" to produce a desired-and-designed overall result that can be scientifically detected — if the data is sufficient and is skillfully analyzed — when we observe an increase of genetic information (and biological complexity) that could not be produced, with a reasonable probability, by undirected natural process. If this occurred, would we categorize the design-action as Ns (undetectable) or Ds (detectable)?
This type of doubt — when we wonder "is it detectable? have we detected it?" — is one reason, among others, that scientists cannot prove design or non-design. { The question, "Can we observe divine guidance?", is examined more closely in a page comparing Progressive Creation and Evolutionary Creation. }

Defining Design-Action ( What about intelligence & intention? )
Although non-design and design are mutually exclusive, in some situations (but not those typically being debated) there is a "gray area" in defining whether there is or isn't intelligent design-action. For example, it can be difficult to define design-action when we have questions about intelligence or intention:
intelligence: The Hoover Dam is obviously a result of design-directed action, but what about a beaver dam? When a beaver builds a dam, a bird builds a nest, or ants build an anthill, is the feature (dam, nest, or hill) a result of intelligent design-directed action? There is action, but should we consider this to be "intelligence at work" or just the undirected natural process of creatures doing "by instinct" what they naturally do? What degree of intelligence is necessary for calling it "intelligent design-action"?
intention: If a company dumps untreated waste-chemicals into a river and changes its ecosystem, is this change a result of design-directed action? The results cannot be explained without considering the "extra chemicals" dumped into the river, but should we define this to be design-action if the dumping was unintentional? if the dumping was a conscious decision to "trade the ecosystem for company profits"?
These questions — is animal behavior due to instinct or intelligence, and how much intelligence is required for design? is intention required for design, and how should we define the unintended effects of an action? — can be interesting, and perhaps we can define "types of design" or "degrees of design" based on some multi-dimensional system of criteria. But these questions are not important (or even relevant) for the usual issues being debated, such as the origin of carbon-based life or a bacterial flagellum.

Details about Design — Part Two (re: goals & abilities)
In Part 1, I claim that details about design are not necessary in science. Elliott Sober disagrees in page 10 of The Design Argument:
"The problem is that the design hypothesis confers a probability on the observation only when it is supplemented with further assumptions about what the designer's goals and abilities would be if he existed. ... There are as many likelihoods as there are suppositions concerning the goals and abilities of the putative designer. Which of these, or which class of these, should we take seriously? / It is no good answering this question by assuming that the eye was built by an intelligent designer and then inferring that the designer must have wanted to give the eye features F1... Fn and must have had the ability to do so since, after all, these are the features we observe. For one thing, this pattern of argument is question-begging. One needs independent evidence as to what the designer’s plans and abilities would be if he existed; one can't obtain this evidence by assuming that the design hypothesis is true (Kitcher 1983; Sober 1999)."

This claim does have some validity, since "goals and abilities" can be useful criteria during an investigation of design.
But a lack of "independent evidence" about "goals and abilities" does not eliminate the possibility that a design inference can be supported by evidence and logic, because if a design inference is logically justified then it will also be logically justifiable to "infer that the designer must have wanted to give the eye features F1... Fn and must have had the ability to do so since, after all, these are the features we observe."
For example, imagine that we observe a radio signal containing a long string of prime numbers (2, 3, 5, 7, 11, 13, 17,...) and our inference to the best explanation is that design-directed action is the best explanation of this observation. This design theory is a scientific inference based on observation and logic and is not, as implied by Sober, the result of simply "assuming that the eye [or signal] was built by an intelligent designer." A design theory about the signal would be a logical inference, not an assumption.
Logically, this design inference must include assumptions that the "signal designer" had the technological capability to produce the signal, the cognitive ability to understand prime numbers, and a motivation to encode these numbers into a radio signal. The mere fact that the signal is being observed makes these assumptions logically justifiable-and-necessary in a design theory.
A claim that we cannot make these logically justifiable assumptions (about capability and motivation) is a claim that this logical "inference to the best explanation of observations" is not scientific, even though explanatory inference is the foundation of all explanatory theories in science.

A Backward Look at Future Science: Are we made from stardust?
In 1600, scientists didn't know whether one element could be converted into another. Now we know, with a high level of confidence, that the answer is no and yes. No, we cannot convert lead into gold by using the methods proposed in 1600. Yes, a supernova can naturally convert hydrogen into gold. In 2000, we confidently declare the extreme improbability (the impossibility?) of one conversion method because of what we do know, not due to the ignorance of what we don't know. But the "future science of 1600" — the principles of nature that we didn't know in 1600 but do know in 2000 — has also helped us understand that we are made of the dust released from stars, which converted hydrogen into carbon, nitrogen, oxygen, and all other atoms in the earth and in our bodies.
In the future of science, will we find the origin of life to be more like a process that — based on reliable scientific theories — we scientifically claim is extremely improbable (like a natural "unmixing" of purple water into the red and blue waters that produced it) or a process (like the conversion of hydrogen into oxygen) that seemed extremely improbable until we learned more about nuclei and stars?

Paradoxical Virtues: Flexibility and Perseverance
Robert McKim, in his book about Experiences in Visual Thinking, discusses the paradoxical virtues of perseverance and flexibility: "When should you abandon one strategy to try another? When is perseverance a virtue, and when is flexibility? Sometimes dogged persistence in the use of a single strategy yields a solution: despite frustration and fatigue, the thinker rattles the same key in the door until it opens. On the other hand, it may simply be the wrong key. When staying with one strategy pays off, we call it 'perseverance'; when it does not, we call it 'stubborn inflexibility.' Genius is often associated with the ability to persevere or, in Edison's terms, to perspire. Creativity is also linked to the ability to be flexible. Clearly, we are facing a paradox. Perseverance and flexibility are opposites that together form an important unity."