Tyrrell_McAllister comments on But Somebody Would Have Noticed - Less Wrong

36 Post author: Alicorn 04 May 2010 06:56PM

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Comment author: Tyrrell_McAllister 05 May 2010 08:21:51PM *  1 point [-]

Okay, I see. I see nothing obviously contradictory with this.

From a technical standpoint, the hard part would be to give a useful criterion for when a seemingly-well-formed string does or does not completely define a predicate. The string not(X(X)) seems to be well-formed, but you're saying that actually it's just a fragment of a predicate, because you need to add "for X not equal to this predicate", and then give an addition clause about whether this predicate satisfies itself, to have a completely-defined predicate.

I guess that this was the sort of work that was done in these non-foundational systems that people are talking about.

Comment author: cousin_it 05 May 2010 08:50:30PM *  1 point [-]

I guess that this was the sort of work that was done in these non-foundational systems that people are talking about.

No, AFA and similar systems are different. They have no "set of all sets" and still make you construct sets up from their parts, but they give you more parts to play with: e.g. explicitly convert a directed graph with cycles into a set that contains itself.

Comment author: Tyrrell_McAllister 05 May 2010 09:17:42PM *  0 points [-]

No, AFA and similar systems are different.

I didn't mean that what you propose to do is commensurate with those systems. I just meant that those systems might have addressed the technical issue that I pointed out, but it's not yet clear to me how you address this issue.