Logic vs Evidence

[Alex K]

Perhaps we are missing Dimaniac's question entirely.

Can a conclusion both sound and valid contradict reality?

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

Formally, the relation A=>B always yields "True" when A is false.