Former Federal Reserve Chairman Alan Greenspan once doubted his own existence.

A friend had to convince Greenspan that he actually existed prior to a meeting with Ayn Rand in the 1950s.

Nathaniel Branden told the story about Greenspan in the BBC 2 documentary "All Watched Over By Machines Of Loving Grace," according to The Spectator. Part one of the three part series premiered Monday.

"You have to realize that Alan Greenspan was, and is, a brilliant mind doing brilliant things in the real world but in his 20s he is sitting with me in my apartment telling me that he cannot say with certainty that he exists, he cannot say for certain that I exist and he cannot say for certain that this conversation exists," Branden recalled.