The filmmaker admits casting The Bourne Identity star in the low-budget drama was "surprisingly easy", because he was ready and willing to do whatever was required of him.
Gilliam explains, "I called Matt and said, 'I've got a small part for you, probably four or five days, I'll send you the script.' He said, 'Don't bother, I'm in.'"
And Damon wasn't the only star who signed on to work with Gilliam without a script read or an agreed salary - Tilda Swinton and Skyfall actor Ben Whishaw also jumped at the chance to team up with the eccentric Monty Python legend.
He adds, "(Tilda and I) had met at different festivals and always said we ought to work together, Ben Whishaw, the same thing. And basically I just called them and they all just came and they worked for scale, that's how we made the film, because we didn't have the budget."
The Zero Theorem centres on a reclusive computer hacker, played by Christoph Waltz, who attempts to discover the reason for human existence.