Comp Sci - Natural Deduction..

gam3r · 8 Jan 2009 at 20:55

Well...I'm not sure where to post this, but i think i will get the most replies here..

I'm finding natural deduction really, really tough especially formulae with ¬(negation) in it! Can anyone help me with this example, i don't understand the whole subcomputation box! Here is one my questions along with the answer. Why are we looking for Q,P,¬P in the first subcomp box? :confused:

If anyone can help, it would be very much appreciated.

shifty_uk · 8 Jan 2009 at 20:58

Could someone help me collect my brain from the floor? My heads just exploded.

Voltar · 8 Jan 2009 at 20:59

How to give Voltar migrane in ten seconds by gam3r... :eek:

good luck with whatever that is/means

gam3r · 8 Jan 2009 at 21:01

Lol yea, it's doing my nut in as well :O

mleh · 8 Jan 2009 at 21:04

Ahh, i did a logic module last year for my course. SOO hard.

Have you tried looking at truth tables for the various connectives(i've forgot their technical name)?

J.B · 8 Jan 2009 at 21:11

I have no idea what's going there so here is a selection of smilieys for you

gam3r · 8 Jan 2009 at 21:13

mleh said:
Ahh, i did a logic module last year for my course. SOO hard.

Have you tried looking at truth tables for the various connectives(i've forgot their technical name)?

Truth tables are are not part of this model, this is syntactical proof system, no truth tables needed!

mleh · 8 Jan 2009 at 21:16

You're looking for Q (second sub box) to prove P (first sub box), and you need to use P and ~P to do it. Since you have a contradiction of P, you can pose anything (Q), IIRC.

You need to look at all the relevant proofs for the connectives first to understand what's going on

^^they're not needed but sometimes they help.