On 07 Nov 2008, at 15:57, Mirek Dobsicek wrote:

##
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>
> Bruno Marchal in an older post wrote:
>>> Also,
>>> can you elaborate a bit more on the motivation behind category
>>> theory?
>>> Why
>>> was it invented, and what problems does it solve? What's the
>>> relationship
>>> between category theory and the idea that all possible universes
>>> exists?
>>
>>
>> Tim makes a very genuine remark (but he writes so much I fear that
>> has
>> been unnoticed!). He said: read Tegmark (Everything paper), then
>> learn
>> category, then read again Tegmark. Indeed I would say category
>> theory has
>
> Bruno, which of the Tegmark's 'Everything papers' did you have in
> your mind?
I guess it is this one:
http://space.mit.edu/home/tegmark/index.html
But it looks the paper is alive and evolves. I was thinking of its
diagram of mathematical structures.
Category theory put "natural" order in mathematical theories.
But recursion theory is a sort of obstacle. category theory works
well for sort of first person recursion theory (like with
realizability, typed lambda calculus/comobinators, etc.)
Then category is a must for knots and geometry ...
Well come back,
Bruno
http://iridia.ulb.ac.be/~marchal/
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