Douglas_Knight comments on Money pumping: the axiomatic approach - Less Wrong

12 Post author: Stuart_Armstrong 05 November 2009 11:23AM

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Comment author: Douglas_Knight 16 November 2009 11:53:49PM 0 points [-]

So what did you mean by

Note, setting the limit to "no preference" does not resolve the discontinuity. But by intermediate value, there will exist at least one such point in any continuous approximation of the discontinuous function.

Comment author: MendelSchmiedekamp 17 November 2009 04:52:36PM 0 points [-]

I meant that setting the limit to no preference for a given C doesn't equate to a globally continuous function. But that when you adjust your preferences function to approximate the discontinuous function by a continuous one, the result will contain (at least one) no preference point between any two A < B.

Now perhaps there is a result which says that if you take the limit as you set all discontinuous C to no preference, that the resulting function is complete, consistent, transitive, and continuous, but I wouldn't take that to be automatic.

Consider, for example, a step discontinuity, where an entire swatch of pA + (1-p)B are stuck on the same set of < and = mappings and then there is a sharp jump to a very large set of < and = mappings at a critical p'. If you map the ordinals to the real line, this is analogous to a y-coordinate jump. To remove this discontinuity you would need to do more than split the preferences at p' around no preference, because all this does is add a single point to the mix. To fully resolve it, you need to add an entire continuous curve, which means a process of selecting new A, B, and C, and showing that the transfinite limit always converges to a valid result.