Here's what we know about him:
* He's a recluse: He only communicates through the classified ad, which he uses to answer people's questions about the meaning of life.
* He's cryptic: His answers are often vague and open to interpretation, leaving Jeremy and the reader to ponder their meaning.
* He's a guide for Jeremy: Though his answers are often confusing, they challenge Jeremy to think differently about the world and his own life.
Mr. Oswald's identity is never fully revealed in the book. This adds to the mystery and encourages the reader to reflect on the meaning of life themselves.
It's left up to the reader to decide who or what Mr. Oswald represents, whether it be a wise old man, a fictional entity, or even a part of Jeremy's own subconscious.