In terms of logic and truth tables why is it that the truth table for exclusive or is as follows:
Consider $P$ and $Q$. Let $P + Q$ denote exclusive or. Then if $P$ and $Q$ are both true or are both false then $P + Q$ is false. If one of them is true and one of them is false then $P + Q$ is true. By exclusive or I mean $P$ or $Q$ but not both. I have been trying to figure out why the truth table is the way it is. For example if $P$ is true and $Q$ is true then no matter what would it be true?
The exclusive or operation (often xor, also known as either-or) only produces a true value if exactly one of the two statements is true; therefore, it has to be the case that either $P \wedge -Q$ or $-P \wedge Q$ (that is, either $P$ is true and $Q$ is false or $P$ is false and $Q$ is true).
If $P\vee Q$, that is, if $P$ and $Q$ are both true, then $P\wedge Q$ - $P$ or $Q$ - is true, because at least one of $P,Q$ is true, but this is the or operation, not the xor (exclusive or) operation.