Philip's and Clarence's stocking contained a book.

The less said about the item's story and the physicist's reaction to it the better.

But something ought to be said, so let's point out that Philip is currently spending most of his time in the library, surrounded by books and notes, trying to decipher the exact contents of his present.

( Speaking of presents... (aka. backdated goods for Daniel, Tim, Alex, Jean and Yujinn) )