After Mandela what will happen to South Africa?
It was a call-in show - on a topic that is on many minds here these days: the fate of a 94-year-old man lying in a hospital bed in Pretoria, and the fate of South Africa once he is gone.
For years people here have been understandably reluctant to discuss the death of Nelson Mandela - out of a profound respect for the man who, more than any other, steered this country from apartheid to democracy.
But the passage of time, and the health scares of recent months - have nudged the issue away from the shadows.
The man on the radio was a black South African from a poor township, and he was articulating a belief that has gained a small level of currency here: that Mr Mandela's passing will unleash not just grief and nostalgia, but a violent rage against the poverty and inequality that still exists here, two decades after the end of white minority rule.
There is, certainly, anger in the country.
Recent headlines have highlighted violent industrial action, the massacre at the Marikana mine, the death of a man dragged behind a police van and the enduringly high crime statistics.
The theory goes that - even from his hospital bed - Mr Mandela exerts some sort of restraint on a on, almost a decade after he retired from public life.
No, in almost every way South Africa is already well into the post-Mandela era.
