Ignoratio Elenchi - The Irrelevant Conclusion

[Tempus]

"Ignoratio elenchi", (from latin, literally meaning "ignorance of proof") is an informal fallacy. It is committed when an argument is made that is not relevant to the point being discussed, even though the argument itself may be valid. Related to red herrings in that both can distract from the issue at hand. A person may ask "what's that got to do with the price of tea in China?" upon encountering this fallacy. Consider the following example where two people are debating whether drugs should be legal or not:

• Person A: "If drugs were legalised criminals wouldn't be able to sell them anymore due to competition from legal sources. Drug wars and other drug related crime would be reduced and less people killed as a result. Keeping drugs illegal causes more problems than it solves."
  Person B: "Yeah, but people would still find something else to kill each other over."
  

In the example above Person B has committed the ignoratio elenchi fallacy. Their point about people killing for reasons other than drugs, while perhaps true, is unrelated to whether drugs should be legal or not. It does not address the points made by Person A. Here is another example:

• Person A: "Humans and chimpanzees evolved from a common ancestor. Here is evidence X, Y and Z."
  Person B: "Hitler was a social Darwinist and used eugenics to try and create a master race. Many people were killed as a result. Here is evidence X, Y, and Z."
  

Person B has again proved a point unrelated to the matter at hand. The truth value of the theory of evolution is independent of the applications it's used for / used to justify.

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• References:
  http://en.wikipedia.org/wiki/Ignoratio_elenchi
  http://www.merriam-webster.com/dictionar...%20elenchi
  http://philosophy.lander.edu/logic/ignoratio.html
  http://www.sccs.swarthmore.edu/users/08/...enchi.html

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I hope you guys find this useful. Please feel free to critique what I've written.