Thursday, August 23, 2012

Bad Argument: the shifting goalpost

The best example of "shifting goalpost" is the "No True Scotsman" fallacy. However, there are many others. It's such that they are very popular fallacies used by defenders of suspect schemes, when they need to "revise" their statement when critics point out holes in their reasoning or evidence.

The proper name for this fallacy is "ad hoc rescue", where the arguer keep revising the original argument by adding more and more exceptions. Though the term "shifting goalpost" is a better visual metaphor. It may take a form similar to this. 

B: You can make legally a ton of money with Acme XYZ! Just work the system!
A: But Acme XYZ requires you to put in money first. That's investment, not work. 
B: Uh, right! Invest in Acme XYZ and make lots of money!
A: But Acme XYZ insists they are not an investment. Says so here _______.
B: Uh... You just don't understand the system! It's new hybrid! 

B just keep changing his argument that he got backed into a corner, and had to invent some new sh__.

Sometimes, the exception list are so long, the revised argument looks absolutely ridiculous. In fact, this is often used for humorous effect, as the following example shows:
Except for sanitation, medicine, education, irrigation, public health, roads, and public order, what have the Romans done for us? 
Well, actually that's quite a list of accomplishments for the Romans.

The problem with this argument is it need to be done over multiple engagements, so someone comitting this fallacy may not have "noticed" it. Or the opponent may not have realized that it was being used.

If you want to give your opponent a "nudge", you can force your opponent to add on more and more exceptions. Then summarize the exceptions to show that he had been using "ad hoc rescue" all along, as his goal keep shrinking and shifting. There are just too many exceptions for his argument to really mean anything. instead of this general statement, it is now such a specialized case that rarely if ever happens.

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