RE: Logic vs Evidence
November 7, 2014 at 10:32 am
(This post was last modified: November 7, 2014 at 10:32 am by genkaus.)
(November 6, 2014 at 7:15 pm)BrianSoddingBoru4 Wrote: Of course it can. If the premises are false then the conclusion is false, but can be bother logically sound. It is important to remember that in logic, 'sound' only means that the conclusion does not contradict the premises - 'sound' isn't the same as 'true'. This is the classic example:
P1. Socrates was a mammal.
P2. All mammals are cats.
C. Socrates was a cat.
Here, the problem is with P2. Thus the conclusion ('Socrates was a cat') is sound, as it follows necessarily from the premises. However, since premise 2 is demonstrable false (not all mammals are cats), the conclusion cannot be true.
Boru
You are confusing soundness and validity
http://en.wikipedia.org/wiki/Soundness Wrote:An argument is sound if and only if
The argument is valid.
All of its premises are true.
Here, P2 is false which makes the argument valid but unsound.
Edit: I see Cato beat me to it.