The Discovery Institute Affirms the Consequent

Is intelligent design science? Scientists think not, but the Discovery Institute’s Casey Luskin disagrees. In a post at the Evolution News and Views blog (reprinted in the Winter 2012 edition of the Discovery Institute’s “The Viewpoint” newsletter), Luskin argues that intelligent design is science

because it uses the scientific method to make its claims. The scientific method is commonly described as a four-step process involving observations, hypothesis, experiments, and conclusion.

I found Luskin’s a fascinating piece because–seemingly unaware of what he’s doing–he defends intelligent design’s status as science by showing that intelligent design is also a logical fallacy. Specifically, it’s a textbook case of affirming the consequent.

Luskin starts by noting the basic observations intelligent design is built upon.

ID begins with observations that intelligent agents produce complex and specified information (CSI). (An event is complex if it is unlikely, and specified if it matches some independent pattern.)

For the sake of clarity, instead of referring to “complex and specified information,” I’m just going to call them “complex creations.”

So, from Luskin’s first point, we can observe that intelligent designers create complex creations. Thus, if we have intelligent designers, we’ll see complex creations. Which sounds right to me.

To keep things simple, let’s give “intelligent designers” the label P. And lets give “complex creations” the label Q.

Thus the first premise of Luskin argument takes the form of “If P, then Q.” (If there are intelligent designers, then there will be complex creations.)

Fair enough. Next, Luskin shows how we can test whether life shows characteristics of a complex creation.

Experiment: Scientists then perform experimental tests upon natural objects to determine if they contain complex and specified information. One easily testable form of CSI is irreducible complexity, which can be tested and discovered by experimentally reverse-engineering biological structures through genetic knockout experiments to determine if they require all of their parts to function. Mutational sensitivity tests can also be used to identify high CSI in proteins and other biological structures.

Conclusion: When experimental work uncovers irreducible complexity, or high CSI in biology, researchers conclude that such structures were designed.

So life is a complex creation. This means life is Q. Again, fair enough. Life certainly is complex. And even the believer in evolution can safely think of life as a “creation” if he’s willing to say that evolution created life.

But here’s where Luskin gets into trouble. His next move is to use the existence of Q (complex creation) as proof of the existence of P (an intelligent designer). We know that intelligent designers create complex creations. Therefore, Luskin argues, if we find that life is a complex creation, we can know that life had an intelligent designer.

Put in our P and Q structure, Luskin’s argument looks like this:

  1. If P, then Q.
  2. Q.
  3. Therefore, P.

Which is, like I said above, the textbook form of the fallacy of affirming the consequent. Just because we know that P inevitably leads to Q does not mean we know that the presence of Q entails there must be a P. It’s entirely possible that things other than P lead to Q.

If it’s raining outside, my windows will be wet. But seeing that my windows are wet does not necessarily mean it’s rain. Instead, I could have left the sprinkler on, or a neighborhood kid could’ve sprayed the windows with the hose.

What’s particularly interesting is that Luskin (perhaps unconsciously) tries to get out of this by making an even weirder move. He has to do away with the non-rain explanations for why the windows are wet. So he writes that, “in our experience, intelligence is the only known cause of [complex creations].”

Luskin’s saying, as did William Paley in his famous watchmaker argument, that every time we’ve seen complex creations in the past, there’s been a designer. We see a complex watch, we know there’s a watchmaker. So if we see complex life, we can assume there must be a designer.

Except, of course, complex life might very well be–and probably is–evidence of complexity without a designer. Luskin’s assuming the truth of his hypothesis (complexity means designer) prior to evaluating the evidence for or against the hypothesis.

So, to summarize, here’s the argument Luskin thinks proves intelligent design’s status as science:

  1. I observe that complex creations have intelligent designers.
  2. From this I hypothesize that any complex creation I find has an intelligent designer.
  3. I go out in the world and find evidence that life is a complex creation.
  4. From this I conclude–though remaining open to refutation–that life has an intelligent designer.
  5. I remain open to refutation because, of course, I may be presented with evidence of complex creations that lack an intelligent designer. I just haven’t seen any such evidence yet.

To which the scientist replies, “But Luskin, you’re surrounded by evidence of complex creations lacking a designer. In fact, you, Casey Luskin, are yourself evidence of a complex creation without a designer.”

Luskin’s response? “But, Mr. Scientist, life can’t be evidence of an undesigned complex creation. Because complex creations require an intelligent designer.”

In other words, Luskin claims his initial observation is true because it’s true, and any evidence to the contrary isn’t really evidence to the contrary because his initial observation is true.

Which doesn’t sound much like science to me.


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  1. Of course not. It’s a religion.

    • Right, but that’s not why Luskin’s argument fails. We could strip all the religious elements out of it and the form of the argument still wouldn’t work.

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