All people in a certain island are either 'Knights' or 'Knaves' and each person knows every other person's identity. Knights never lie, and Knaves ALWAYS lie.
$P$ says "Both of us are Knights". $Q$ says "None of us are Knaves".
Which one of the following can be logically inferred from the above?
- Both $P$ and $Q$ are knights.
- $P$ is a knight; Q is a Knave.
- Both $P$ and $Q$ are Knaves.
- The identities of $P, Q$ cannot be determined.