Wrong and Irrelevant

Recognizing and defeating a common rhetorical device.

Misc, to-do

In discussion, sometimes one side will make an error of fact. These are easy to point out, and easy to refute. Another common mistake is when the evidence offered is not really relevant to the disputed issue. This one is also easy to address. Each of these attempts at persuasion is weak in itself. The problem is that when they are combined, they can become strong. Or rather, the combination can appear strong unless it's refuted properly.
Here's how it works: Alex says something outrageous or stupid or just plain wrong. Betty reacts and points out a defect in Alex's statement. The problem is that Alex's statement actually consists of two parts, one of which is factually incorrect and the other is irrelevant. If Betty is not careful, and doesn't address both parts, her refutation can appear weak. If she addresses only the factual part, it gives legitimacy to the incorrect assumption that the statement is relevant to the discussion. Likewise, if she only attacks the relevance, it is seen as implying the factual correctness of the other part, thus appearing to be a concession, where in fact it may not be.
Here's an example. In a recent discussion about the merits or demerits of democracy, my correspondent stated that "this nation was never intended to be a democracy." Assume for a moment that "intended" refers to the US Founding Fathers. If I address only the question of whether any of the Founding Fathers advocated democracy, I'm seeming to accept the implied assumption that we should be ruled by what the Founding Fathers intended. On the other hand, if I only address the relevance of their thoughts, I seem to accept the assertion that none of them advocated democracy. Either way, my argument seems weak. My opponent has "won" with two weak arguments joined together, where he would have "lost" if he had presented them one at a time and I had refuted them one at at time.
other examples:

  • homosexuality is a choice
  • abortion is the leading cause of death in the US
  • related to: the soundness of arguments
  • sound = premises true and argument valid
  • when a premise is untrue and the argument is invalid is what I'm on about
  • More examples (I'll add to this list as they occur to me):
    • Since black people are not as smart as white people, it's only fair blacks are poorer than whites.
    • The Satanic Verses is blasphemous, therefore it should be suppressed.
    • Torture works, therefore we should use it.
    • The NSA spying thing is illegal, plus it doesn't work
      • what if it did work?
      • including both, each one weakens the other?
        • reminds me of: religious people making secular arguments that are not crucial to their position. example: suppose I oppose abortion on religious grounds, and one of the arguments I make against it is a secular one: that it causes cancer. if I found out it actually doesn't cause cancer, I would stop using that argument, but I would not change my position. should I have used it in the first place?
        • related: is it acceptable to use an argument I don't buy, if I think my interlocutor might?
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