Three and a half years ago, Terry Pratchett, the beloved author of the Discworld series, announced that he has early-onset Alzheimer's disease. Now he's made an even more startling announcement. Pratchett, who has campaigned in his native United Kingdom for the right of assisted suicide, has begun the formal process of assisted suicide in Switzerland, one of the few countries in the world to legalize euthanasia. Specifically, this would take place at Dignitas, a clinic that provides qualified doctors and nurses to assist with the patients' suicides. Dignitas has sent Pratchett the paperwork he needs to sign to begin the...