Imagine you took out a loan for $1000 in 1980. In today’s dollars, the $1000 to repay is much less in relative terms than it was in 1980, because of inflation.
I'm aware of the implications of inflation and the passing of time. Let me be more direct. The "correspondence" between federal deficits and inflation Walter implied existed was almost certainly pulled from his cushions. A deficit that _purchases_ an increase in the money supply certainly _can_ lead to inflation, among other deficit sources in varying degrees. But the implication that we pay for deficits specifically with inflation is a gross oversimplification, all in service of being pithy.