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?

1. Both $P$ and $Q$ are knights.
2. $P$ is a knight; $Q$ is a Knave.
3. Both $P$ and $Q$ are Knaves.
4. The identities of $P, Q$ cannot be determined.