wedrifid comments on The Amanda Knox Test: How an Hour on the Internet Beats a Year in the Courtroom - Less Wrong

42 Post author: komponisto 13 December 2009 04:16AM

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Comment author: wedrifid 16 December 2009 02:57:56AM *  3 points [-]
  1. The house has been reduced to a pile of charred debris -> There was a fire.
  2. The house has been reduced to a pile of charred debris -> There was arson.

Anna would obviously call 2) a leap but not 1). I am aware that a similar process of inference is involved, differing only by degree and yet I am still able to grasp what Anna is trying to say. That Anna has explained what she is trying to say multiple times helps, as does my IQ. Yet I don't think either of these things are required to get at least some idea of the intended meaning and certainly don't get the impression that you lack the intellectual resources to do so yourself, should you desire. Agreement, of course, is a different matter.

I will make these observations:

  • Evidence of a break in increases p(staged break in).
  • Evidence that the break in was staged increases p(guilt).

One line of reasoning is this:

  • Evidence of a break in increases p(a break in was staged).
  • Evidence that a break in was staged increases p(guilt).
  • There is evidence of a break in.
  • Therefore, the evidence of a break in increases p(guilt).

This does not follow. Evidence of a break in decreases p(guilt). That is precisely why someone would have motive to stage a break in! Anyone who attempted to increase the extent to which the above fallacious reasoning was applied would be doing something I disapproved of strongly.

Comment author: brazil84 16 December 2009 10:30:13AM 0 points [-]

"The house has been reduced to a pile of charred debris -> There was a fire. The house has been reduced to a pile of charred debris -> There was arson. "

Well, what if a house has been reduced to a pile of charred debris and traces of some volatile flammable liquid are found there? It seems to me that by Anna's reasoning, it would be a "leap" to say that this is evidence of arson. And yet most reasonable people would agree that this is evidence of arson.

Anyway, I would appreciate it if you would assume I am trying to discuss this in good faith.

"One line of reasoning is this:

Evidence of a break in increases p(a break in was staged). Evidence that a break in was staged increases p(guilt). There is evidence of a break in. Therefore, the evidence of a break in increases p(guilt). "

I'm not sure that anyone is making that argument here. At any rate, I am not.

Comment author: wedrifid 16 December 2009 10:43:48AM *  0 points [-]

Well, what if a house has been reduced to a pile of charred debris and traces of some volatile flammable liquid are found there? It seems to me that by Anna's reasoning, it would be a "leap" to say that this is evidence of arson.

That would be evidence of arson. Anna's reasoning would not call this a leap. As a reminder, the position of Anna's that you were refuting in this branch of comments is this:

To have evidence of a break-in is different than having evidence of a staged break-in. Since there is evidence of a break-in, but not any that would say it was staged, there is evidence of an invented idea of a staged break-in.

You disagree elsewhere with the premise but here you are arguing against, and misunderstanding (whether motivated or not), the argument.

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