You are a thief! I can prove that you, the reader, stole $20 from me. Last night, while my wife was out of town, I left a $20 bill on the kitchen table. When I woke up this morning, there was no $20 bill on the table. Since I didn’t take the bill, you must have stolen it. I am sure you will deny the theft, but I insist that I had nothing to do with removing that bill from the table.
Have I proven that you stole the bill? If you think my logic is ok, then please forward $20 to my address in small unmarked bills. If not, then you can save yourself $20 by reading on.
In fact there is something wrong with my logic, isn’t there? My bogus proof is based on a logical fallacy that goes by a number of names. It is variously called false dilemma, false dichotomy, the either-or fallacy, fallacy of false choice, black-and-white thinking, fallacy of exhaustive hypotheses, or excluded middle. As you can see by the descriptive names, the fallacy is based on the implicit assumption that there are only two explanations or two possibilities. The logical form would look like:
- X is true if Y is false.
- Y is false.
- Therefore X is true.
or in our case:
- Either I removed the money or you stole it.
- I did not remove the money.
- Therefore you stole it.
As you can see, conclusion #3 is not proven unless premise #1 is proven. And in our case, all I did was falsely assume in #1 that there could be only two explanations for the missing $20. I created a false dichotomy with a list of only two explanations involving either me or you. And I excluded from the middle of the list all the other possible thieves in the human population and all the other non-criminal explanations for the missing money. (I did this hoping you would not notice the logical sleight of hand and each of you would send me $20 as restitution for your obvious criminal activity. )
Notice that although there could be billions of possibilities for why the money was gone including that it simply blew off the table and the dog is lying on it. But it makes no difference to the proof that you or I can think of any or not. The burden of proof lies with the accuser. And this proof fails on the false dichotomy before we even start to think of other possibilities. (I am not saying that the proof is false, but that the logic doesn’t demonstrate that it is true.)
If you are having trouble seeing the problem with this logic, consider that I can substitute the you-as-thief hypothesis for any fanciful one I can dream up.
- Either I removed the money or a magic unicorn took the money.
- I did not remove the money.
- Therefore a magic unicorn took the money.
Now if this logic actually can prove where the money went, then both explanations would have to be true. The false dichotomy offers no evidence for either the “you as thief” or the magic unicorn theory. All it relies on is the me-removing-the-money hypothesis being false. So if one is true, then so is the other. By faulty logic, we have demonstrated that both you and the magic unicorn took the money.
Now it would be legitimate to say that one explanation is more likely than the other. It might save us time to simply ignore the unicorn hypothesis in our forensic examination. But what is likely or unlikely is not the point here. The point is whether the logic by itself proves the conclusion or not. And as we can see, false dichotomy logic can “prove” any fanciful explanation that we can dream up based only on the one hypothesis we know is wrong ( me removing the money, for example). And any logic that can prove anything to be true proves nothing.
Appeal To Ignorance
But since my last proof failed, I now I have a better proof regarding my stolen money. I claim that a magic unicorn stole my $20. This time my logic is that no one has yet provided me with evidence that it was not a unicorn. You see, if you can’t demonstrate to me that a magic unicorn did not steal my money, haven’t I proved the hypothesis?
Of course not. I provided no positive justification for the unicorn hypothesis. All I did was appeal to our current ignorance one way or the other about the unicorn thievery. This logical fallacy is called an Appeal To Ignorance, or Argument From Ignorance. It has the logical form:
- X is true because if we have no evidence that it is not true.
- We have no evidence that X is not true.
- Therefore, X is true.
or in our case:
- A magic unicorn stole my money if we have no evidence that he did not.
- We have no evidence that a magic unicorn did not steal my money.
- Therefore a magic unicorn stole my money.
As you can see again, the conclusion (#3) fails because premise #1 fails. What is missing is any positive evidence in support of the unicorn hypothesis. It relies only on an appeal to our ignorance of any evidence for or against the unicorn hypothesis.
These two logical fallacies, False Dichotomy, and Appeal to Ignorance and many others have been well understood to be bogus ever since the ancient Greeks developed the intellectual discipline of logic and rhetoric. In fact we still use the Latin names for most of them because they come down to us through antiquity. Every college student who takes a course in logic and rhetoric should be able to identify these logical fallacies in someone elses argument and call them out on it right away.
Irreducible Complexity and Intelligent Design
Which brings up the question of why these logical fallacies lie at the heart of one of the pillars of the argument for Intelligent Design put forth by author Michael Behe in his book in the popular press called Darwin’s Black Box: The Biochemical Challenge to Evolution.
In the upcoming Part 2 of this 3 part series I will show that the notion of Irreducible Complexity and its relationship to the Intelligent Design Inference is based on the same logical fallacies we learned about in this post, which is the main reason why the scientific community has rejected it as pseudo-science.