[hist-analytic] Knowing that I know a Necessary Truth

Baynesr at comcast.net Baynesr at comcast.net
Sat Jan 1 12:52:37 EST 2011

Here is part of what Danny may have in mind; not sure. 

'(F)(x)(y)(x=y->Fx iff Fy)' 
'(F)(a=b. -> Fa iff Fb)', substituting 'Nec...=a' for 'F' 
'a=b->Nec.a=a iff Nec. b=a)', and so 
we get by df. of 'iff' 
'a=b -> (Nec. a=a -> Nec. b=a)' 
So, given 'Nec. a=a' we arrive at 
'a=b->Nec. b=a', by conditional proof. 
Thus, if 'a=b' then 'Nec. a=b'. 



----- Original Message ----- 
From: "Roger Bishop Jones" <rbj at rbjones.com> 
To: "hist-analytic" <hist-analytic at simplelists.co.uk> 
Sent: Saturday, January 1, 2011 10:47:12 AM 
Subject: Re: Knowing that I know a Necessary Truth 

On Wednesday 29 Dec 2010 19:08, Danny Frederick wrote: 

> Take 'Hesperus = Phosphorus,' for example. If it is true 
> it is a necessary truth (assuming Hesperus exists). 

I am interested to know: 

a) whether the term "necessary" in the above is 
intended as ordinary English or as a philosophical 
term of art 
b) in either case, what you understand it to mean 
c) what grounds you have for believing your claim? 

Roger Jones 
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