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FAQ: Is it appropriate to justify intelligent design theory via analogies?

a.k.a. You can't argue for biological (rarefied) design using examples of human (ordinary) design.

The Short Answer: Arguments by analogy can be valid if there is sufficient similarity between the case in the analogy and the actual case. Intelligent design theory postulates that we can detect design by finding the product of design -- specified complexity. We try to detect intelligently sent signals from space through the "Search for Extra-Terrestrial Intelligence" (SETI) program by looking for specified complexity in the signals. Similarly, determine that archaeological artifacts, such as the heads on Easter Island, were intelligently designed because of their specified complexity. These two examples show how the underlying principle of intelligent design -- that we can detect design through the presence of specified complexity -- is true. If this underlying principle is true, then we can detect design not only in archaeology and SETI, but also in biology, and perhaps in cosmology. The analogies are valid because there is sufficient similarity between their methods of detecting design (i.e. find specified complexity) and intelligent design research in biology (i.e. look for specified complexity). To claim we really only understand human "ordinary" design and thus cannot look for non-human design in biology ("rarefied design") ignores the fact that specified complexity is a fundamental product of all forms of intelligent design--be they human-produced or non-human-produced; biological or non-biological.

misc The Long Answer:

The argument by analogy is an extremely common, and if used properly, completely valid form of argumentation. However, all arguments by analogy are not necessarily necessarily valid, and there are various ways of testing an analogy. Some tests include:
  • Number and quality of examples
  • Counter-examples left out
  • Number of similarities
  • Relevance
  • Dissimilarities
  • Questionable similarities
  • Questionable other traits

    (see Argument by analogy for a full discussion)
  • As Philosophy of Religion states ( "If we are justified in inferring that like cases have like causes, as the argument from analogy suggests, then we can prove more than that the universe has a designer." The same could be said for life. If we can prove that human-based investigations for intelligent design in the non-biological sciences bear a sufficient similarity to investigations for intelligent design in the biological sciences, then we have made a proper analogy.

    A good example for design detection that is analogous to that used with ID in biology are the stone faces on Easter Island. The example for the stone faces on Easter Island is an example of how we go about inferring design. The stones are shaped in a complex and specific way such that we recognize that they are supposed to be faces. Based on this observation, we can infer that they must have been designed. We can determine this even if we don't know who the designers were, how they exactly worked, nor what the intended purpose of the design was. This analogy works because there is complex and specified information (CSI) in the heads of easter island, just like there is CSI in irreducible complex structures found in biology. Although the form of the CSI is different, it is the presence of the CSI that matters, thus the analogy holds.

    Another good analogy of design detection is the Search for Extraterrestrial intelligence. In SETI, researchers search for a complex and specified pattern of electromagnetic radiaton emanating from space. If they find a which matches what they would expect from an intelligent source (such as a series of prime numbers found no where in nature), then they conclude design.

    In both the Easter Island and SETI examples, investigators search for complex and specified information to detect design. This is exactly what intelligent design theorists search for to detect design in biology. The analogy thus seems to hold, at least on this minimal level.

    It has been suggested that this analogy is inappropriate because it is assumes that similarities between inanimate objects (i.e. the stone faces) and biological ones. The purpose of the analogy is not to say that inanimat objects are the same as animate objects (which would thus create a problem of relevance and dissimilarities), but rather is to merely providing an example of a situation similar in nature to the method of detecting design in biology is the same as detecting design in other fields. In other words, the analogy to the stone faces is supposed to exemplify the same type of design inference process and situation that we use in ID for biological systems.

    Finally, one objection put forward by critics of intelligent design is that we understand how humans design human-made objects (i.e. "ordinary design") because we have present-day experience of it. But we don't currently observe non-human designers designing objects in biology, making it "rarefied design," and thus are not justified in inferring design in biology.

    This objection fails to recognize that a fundamental tenet of intelligent design theory is that all forms of intelligent designers produce designs with a common property: specified complexity. The proof behind this claim is simple: intelligent agents are capable of employing choice as they design objects. They are able to think with foresight and mentally figure out solutions to complex problems before actually designing. Thus, intelligently designed objects can contain high levels of complexity which conform to a specific pattern of solution to the problem. Thus we need not have direct observational evidence of how any particular intelligent agent acts: since the agent is intelligent, we already know it will produce specified complexity.

    Alternatively, a counter-response to this objection is that it does not matter if the designer was "human" or "non-human" to make the general argument as follows: "Humans design things with X. If something out there is intelligent like humans, and thus designs things in a similar way to the way we design, then we would also expect to find 'X'. If we find X, we have circumstantial evidence of some intelligence out there acting in the same way we do. This very line of reasoning is fundamental to SETI--there is no proof of the extraterrestrial agent, but we assume that if the extraterrestrial is "intelligent like us" then we might expect to find certain types of intelligently designed radio-signals in space. We then look for them. (SETI researchers haven't found any such signals yet, but they are still looking.)

    Thus, even though we have no present-day visual experience of seeing a non-human intelligent agent currently designing things in biology, we can reason as follows: "If a non-human intelligent agent had a form of intelligence that caused it to design things kind of like humans do, and then we find objects with properties of human-like design in biology, we could assume that they were also designed by an intelligence like our own." Of course that does not mean that all forms of design detected in biology were designed by humans--intelligent design theory cannot tell you anything more about the designer other than that they had a property of intelligence similar to that found in present-day humans.