Can we be certain that A=A?
Can we be 100% certain that A=A and that 1+1=2?
It seems reasonable. 2 is just a symbol for 1+1. We define 2 to be 1+1. They are the same thing, so the statement 1+1=2 is equivalent to A=A, the Law of Identity.
And 'A=A' it isn't really saying anything new. We already knew A was A before we wrote down 'A=A'. This is obviously important because all deductive arguments come down to an A=A claim.
But can we go so far as to say we're 100% sure that A=A? Someone I was talking to suggested that, no matter how logical or self-evident something seems, it's possible that we're making some mental error and are wrong.
It seems we cannot be certain that the results of most deductive arguments are true. I'm sure everyone has occasionally made some 'logic error' in their brain, momentarily believing that a cube has 8 faces for examle. But what I'm talking about is the Law of Identity itself. Can we be certain that something must be equal to itself?