If you didn't see Terry Pratchett's Dimbleby Lecture on BBC TV last night then watch it now.
I'm not sure if this will be visible outside the UK, but I suspect it will be on YouTube very quickly.
Because of his condition, he couldn't deliver it himself and asked his friend Tony Robinson to read it for him. This was itself a remarkable performance, delivered with passion and tenderness, and without once so far as I could see referring to the text in front of him.
Watch it if you can.
EDIT: Here is an extract published in the Independent today.