We skipped ahead in the order to accommodate the release of Thiel's talk, now back in sequence. 
Lecture 3: Counterintuitive Parts of Startups, and How to Have Ideas
a 
Annotated transcript via Tech Genius
Previously:
Y Combinator's Online Stanford Class: "How to Start a Start-up"--Lecture One
Y Combinator's Online Stanford Class: "How to Start a Start-up"--Lecture Two 
Peter Thiel at Y Combinator's Online Stanford Class: How to Start a Startup