A quotation by Roger Penrose
Intelligence cannot be present without understanding. No computer has any awareness of what it does.
Quoted in Des MacHale, Wisdom (London, 2002).
Do not be afraid to skip equations (I do this frequently myself).
Preface to The Road to Reality, (London, 2005)
The subject of quantum gravity came up and Penrose and Feynman got into a heated argument. Penrose said, Feynman was so quick, he was usually about five steps ahead of me at any given point. Sometimes he didn't listen to what I was saying. The whole thing was mentally exhausting. I was completely drained at the end of the session. I have never encountered anyone so quick before. What Penrose and many other physicists didn't realize was the reason that accounted for Feynman's quickness on many matters in physics. Feynman thought about some of these areas in great depth and for long periods of time. A topic like quantum gravity would be one that Feynman had spent countless hours thinking about. It wasn't all off the cuff.