Have the soothing words of Paul Krugman convinced you that the ballooning federal debt is no big deal? Barron’s columnist Gene Epstein offers the following information that might prompt you to change your mind.

“ONE CANNOT BLITHELY IGNORE an internal debt on the ground that ‘we all owe it to ourselves,’ ” wrote Paul Samuelson in the ninth edition of his best-selling textbook, Economics. An “external debt,” in which debt is held by foreigners, brought added burdens, as Samuelson also explained. While the textbook author assured us that the federal debt at “its present level does not merit…psychological excitement,” he cautioned that “recklessness concerning deficit spending and debt formation …could become an important social evil [italics in original].”

Since the most prominent member of the debt-denial club, New York Times columnist Paul Krugman, has called the late Paul Samuelson “the incomparable economist,” I quote his reasonably sensible words on debt and deficits. Last week, Krugman wrote that “debt does not directly impoverish us, because it’s money we owe ourselves…some Americans lent to other Americans….” Perhaps Krugman’s incomparable mentor could provide the columnist with a helpful corrective to his current views.

When Samuelson wrote of the debt’s “present level” in this 1973 edition of his text, it stood at 25% of gross domestic product, a 42-year low. The ratio has been projected to be 76% by the end of this fiscal year in September, a 64-year high, and given the pending explosion of the baby-boomer time bomb, it could easily climb toward 200%. And if internal debt is a not-to-worry because it’s all about some Americans lending to others, then the mountainous mortgage debt that helped bring down the U.S. economy in 2008 should have been a non-event.

BUT IN ANY CASE, NEARLY HALF of the federal debt (the debt held by the public) is now held by foreigners, up from about a third as recently as 10 years ago. So the jump in both the debt and the external debt might have motivated Krugman’s mentor to be a bit more concerned about the “social evil” posed by the debt, had he been writing his textbook today.