Logic vs Evidence

[Mystic]

Depending on how you define logic, logic includes things like belief in a sense of self (that minute ago you, is the same you), belief in other minds, belief things weren't just created a few seconds ago with false appearance of age and false memory, belief in induction and other things.

The fact we have properly basic beliefs on logic doesn't give you the go ahead to believe whatever you want and say it's properly basic though.

However, whether objective morality exists or God exists, stuff like that, can be argued either way.

There are some people who don't believe the physical world exists.

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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

Sound means premises are true and the argument is valid. Rationally, it's impossible for the conclusion not to be true.