What element of life does O'Connell call "the last remaining truth" (4) and why?

O'Connell asserts that in the twenty-first-century world, the only truth that remains undisputed is "the supreme fiction of money" (4). By making this observation, O'Connell is pointing out the irony of a world in which the only thing that can be counted upon is an object with no inherent value at all.