> unfortunately he's unable to present it well. His lectures are almost useless. I don't know; I've listened to dozens of hours of his videos and found them al

> unfortunately he's unable to present it well. His lectures are almost useless. I don't know; I've listened to dozens of hours of his videos and found them all useful and rather clear. I've heard comments like yours from others though, and I guess there are two points: * Of course a person at 80 will not speak the same way they did at 40. (I'm currently watching his lectures on Mathematical Writing, given when he was 49: https://www.youtube.com/watch?v=mert0kmZvVM&index=2&t=0s&list=PLoROMvodv4rOrFl78-o6m_QbJqTXGfVVb https://www.youtube.com/watch?v=mert0kmZvVM&index=2&t=0s&lis... -- youtube has some even older videos on TeX etc but they're probably of less general interest.) Older people generally have more halting speech and the like, but this is perfectly natural. I suspect that if, for cultural or whatever reasons, you haven't spent a lot of time listening to old people and learning from them, you may just find it unfamiliar. Nevertheless, I was in the audience when Knuth gave his 2017 Christmas Lecture weeks before his 80th birthday, and a lot of the audience did seem to follow along and enjoyed it. (You can hear laughter in the expected places in the video: https://www.youtube.com/watch?v=BxQw4CdxLr8 https://www.youtube.com/watch?v=BxQw4CdxLr8 -- so clearly not everyone feels the way you do.) * Every person has their own speech style, their way of translating thought into sounds. Like an unfamiliar accent, it may take a few minutes or hours to get used to it. (If you care enough about the content you will.) What you get from speech idiosyncrasies (their pauses, backtracking, mistakes, etc.) that you don't get from the written word is a window into someone's way of thinking, and I find in Knuth's lectures it's much easier to follow along his thought process, than in speakers you may consider more "smooth". It's very natural and informal, even when he's discussing highly technical topics there's a lot of him that comes through, and that's very valuable IMO. (And his speech seems well within the norm... I've seen comments like yours that sometimes attempt to diagnose medical conditions from afar; that can seem a bit excessive.)