[joebig]

Bang on.. Several thought experiments and constructs he would present in the lectures will elucidate/challenge a foundational concept in such a manner as to lead an inquisitive reader or student on a quest to absorb the extant knowledge just to be able to answer the conundrum satisfactorily. Many of these have since become classics.

[_yb2s]

Yes, another thing Feynman is doing is teaching people how to think about and model problems in a simple but reliable way in their mind, something he was very good at. In a sense his specific subject matter is just an example to demonstrate the process.

A textbook that just plainly presents the facts about a specific phenomenon isn't necessarily training you to think like a theorist, in the way Feynman is.