Is Ra's Al Ghul alive or dead?

Viewers are lead to believe that Ra's Al Ghul died when the train de-railed and crashed into Wayne Tower in Batman Begins.

But he appears to Bruce while he is in the pit during the Dark Knight Rises.

Ra's Al Ghul: "Did you not think I would return Bruce?"

Bruce Wayne: "Ra's?"

Ra's Al Ghul: "I told you I was immortal."

Bruce Wayne: "I watched, I watched you die."

Ra's Al Ghul: "Oh there are many forms of immortality."

Is it just Bruce dreaming or is Ra's truly immortal and did appear to Bruce in the pit?

• Next In the episode "Hide," why does the TARDIS mimic Clara?
• Previous Who is the Lady of the Wood, and what's her relationship to the rest of the elves?