CSI and false dichotomies

Yesterday I watched a CSI: Miami chapter where Erik Delko was accused of smoking marijuana.




South Beach, Miami. Full of marijuana smokers as Delko, most surely. Taken from Wikimedia Commons

What I want to comment on is the short interview of an Internal Affairs officer to Delko’s workmate Ryan Wolfe. The aim of the interview was to find evidence of Delko’s drug comsumption, and it went like this (loosely transcripted):

Officer: – Have you seen Delko consuming marijuana, or any other drug?
Wolfe: – No.
O: – Have you seen Delko in posession of marijuana, or any other drug?
W: – No.
O: – Did you see Delko with any drug-related paraphernalia?
W: – Nothing illegal…
O: – Then, what?
W: – Only cigarrette-paper.
O: – What do you think the paper was for?
W: – Maybe smoking tobacco.
O: – Have you ever seen Delko smoking tobacco?
W: – Never.
O: – Then, the paper was not for smoking tobacco! (clearly implying that it was for smoking marijuana)

Wow! Amazing this guy’s logic!

First, he makes use of a loaded question: asks about Delko smoking tobacco, making the negative answer (that he expects) sound like the assumption that he does smoke marijuana.

Second, he makes an argument from ignorance: since Wolfe has not seen Delko smoking tobacco, Delko does not smoke tobacco.

Third, in doing this he commits false dichotomy: the only uses of cigarrette-paper are not smoking either tobacco or marijuana, and the denial of one option does not make the other true. Inferring that, because we don’t know any other use for that paper, there must be only those two uses would be another argument from ignorance.

Fourth, and most prominently, he is delivering an outrageous non sequitur: he implies that Wolfe not having seen Delko smoking tobacco is a proof of him not smoking tobacco, but Wolfe not having seen Delko smoking marijuana is not a proof of him not smoking marijuana.

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