The very act of invention involves forgetting everything you know. You can’t have a discussion about the future using the words and concepts of the past or present. You have to forget everything you know about the way people interact with a computer and reinvent it, as well, around this new future. Otherwise, you end up asking the wrong questions and trying to see where this new thing fits.
He wrote this in the context of how Microsoft markets Kinect, but I think it's a great quote that applies to pretty much everything in life, not just technology.