A philosopher is a person who works, studies, or is an expert in philosophy. The word, "philosopher", comes from the Greek language and literally means "friend of wisdom". Some famous philosophers include: Socrates, who was a Greek philosopher, Immanuel Kant, who was a German philosopher, and David Hume, who was a Scottish philosopher. One of the most famous philosophical questions is "Is there anything about which we can be absolutely certain"? A quite different question is "Do we have free will"? These, and many other questions, have a long history, and are answered differently by different philosophers.