# Definition talk:Unique

Tarski lumps together uniqueness and "exactly one". According to PW standards, should I give "exactly one" its own page? --GFauxPas 08:24, 25 December 2011 (CST)

no --prime mover 18:09, 25 December 2011 (CST)

## Recategorisation

I'm not sure I agree with the recategorisation.

a) It is a general term used throughout the whole of mathematics, whether in the context of logic or not. (The truism that logic is the basis of the whole of mathematics is not the point here, otherwise everything would go in the "logic" category.) Therefore I believe it belongs in the top-level "Definitions" category.

b) It is categorised in with predicate logic because it has a specific interpretation in that category. That is, it is explained and defined rigorously in the framework of predicate logic rather than propositional logic where quantification is not defined.

c) Also note that the technique for definining uniqueness is so completely universal (assume there are two, then prove those two things are the same) and so really deserves a page based on this one in the "proof techniques" category, but that's another story. --prime mover (talk) 18:42, 9 September 2013 (UTC)

The problem that I had regarded the limitation of "unique" to predicate logic, which is of course not appropriate. Have made it Category:Definitions instead. — Lord_Farin (talk) 21:28, 9 September 2013 (UTC)
Where's the problem with having it in Category:Definitions and Category:Predicate Logic? It has a particular relevance to the latter which makes it appropriate to be placed in that category, it seems to me. --prime mover (talk) 21:48, 9 September 2013 (UTC)
Ah, you have done. --prime mover (talk) 21:52, 9 September 2013 (UTC)
It seems multiple categorisation was an oversight for me this afternoon. Glad we've got it dealt with. — Lord_Farin (talk) 21:55, 9 September 2013 (UTC)