In 1983, when I graduated from the University of California law school in San Francisco in the United States, our commencement speaker was Robin Williams. He had been chosen by the students to deliver the speech.

His speech that day was brilliant. He was irreverent and respectful, as well as funny and serious. When I went to get my diploma, I ignored protocol and walked over to shake Williams' hand. Subsequently, other students did the same thing, and I don't know why - whether it was that break with tradition or Williams' words - but that was the last time the law school allowed students to pick their own speaker.

Too bad. Williams was the consummate pro. He had spent two days on our downtown campus walking around with students, attending classes and had done the necessary research not only into law but our faculty as well. He knew his stuff.

The first e-mail I got about Williams' apparent suicide came from a friend who was charged with recording Williams' speech that day more than 30 years ago. The two of us have listened to the recording of Williams' speech many times over, celebrating his words.

After I learned about Williams' death, I spent Tuesday searching online for his comic routines and found myself once again laughing hysterically for hours while sitting in a Ho Chi Minh City hotel room.

Quite simply, along with Eddie Murphy, Williams was the funniest man I ever heard. He epitomized for me, and many of my contemporaries, the absolute zenith of humor. And this is what makes it so hard to understand his suicide. Here was a man who brought absolute pleasure to millions of people, a man who could send people into paroxysms of pure joy but apparently could not outrun his own demons.

Ironically, my article on suicide was published in China Daily the day Williams' death was made public. And although I've written on suicide for China Daily before, I don't claim to fully understand the phenomenon.

Given the widespread reports about celebrities suffering from depression, people may tend to believe they are more likely to get depressed and even commit suicide. But as frequently happens when one examines evidence scientifically, it's not really clear whether celebrities are at greater risk of going into depression and committing suicide than ordinary people.