JGWeissman comments on How to Not Lose an Argument - Less Wrong

109 Post author: Yvain 19 March 2009 01:07AM

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Comment author: JGWeissman 23 February 2011 08:58:26PM 4 points [-]

Mathematical induction using the first step as the base case is valid. The problem with the horses of one color problem is that you are using sloppy verbal reasoning that hides an unjustified assumption that n > 1. If you had tried to make a rigorous argument that the set of n+1 elements is the union of two of its subsets with n elements each, with those subsets having a non-empty intersection, this would be clear.

Comment author: MoreOn 23 February 2011 09:35:28PM 0 points [-]

Induction based on n=1 works sometimes, but not always. That was my point.

The problem with the horses of one color problem is that you are using sloppy verbal reasoning that hides an unjustified assumption that n > 1.

I'm not sure what you mean. I thought I stated it each time I was assuming n=1 and n=2.

Comment author: Nebu 13 December 2015 06:22:26AM 0 points [-]

The problem with the horses of one color problem is that you are using sloppy verbal reasoning that hides an unjustified assumption that n > 1.

I'm not sure what you mean. I thought I stated it each time I was assuming n=1 and n=2.

In the induction step, we reason "The first horse is the same colour as the horses in the middle, and the horses in the middle have the same colour as the last horse. Therefore, all n+1 horses must be of the same colour". This reasoning only works if n > 1, because if n = 1, then there are no "horses in the middle", and so "the first horse is the same colour as the horses in the middle" is not true.