I sat through some of these lectures once upon a time. If you didn't listen with full attention you got lost in a hurry and there was no going back. I still like the content because it is a challenge to think about it. I like it more because the guy, Richard Feynman is a hero and so completely fluid in something...its like you would talk about aspects of your spouse or child or grandchild...you are so "into that" so you can just talk about it with complete ease of knowledge. See my prior post on Kismet and the French Philosopher who talked about particles...Feynman must have really run into some good stuff.