What it is
The old joke: a heckler insists the Earth rests on a turtle. What holds up the turtle? Another turtle. And that one? “It’s turtles all the way down.”
That’s an infinite regress. David Deutsch’s point is that it’s a bad explanation not because it fails to explain everything, no theory does, but because what it leaves unexplained is the same thing it claimed to explain. A designer designed by another designer, forever, is another example. So is delegating your work to someone who delegates it to someone else.
How it shows up for me
I see it in meetings. “The process will handle it.” Who handles the process? When the answer is another process, nobody is actually responsible.