Kudos to Duff McDonald for his op-ed “Harvard Business School earns an incomplete in ethics’’ (Opinion, Sept. 25). My only caveat is his insertion of the old cliche of “the Protestant ethic.’’ To be sure, reformers such as Martin Luther and John Calvin did indeed assert that “the ability to accumulate wealth is a reflection of one’s character,’’ but it is the character of sin and greed, not virtue.

As Luther noted in one of his many writings against early modern capitalism, “How skillfully Sir Greed can dress up to look like a pious man if that seems to be what the occasion requires, while he is actually a double scoundrel and a liar.’’ Luther’s lifelong criticism of unregulated capitalism was rooted in his analysis that it divorced money from human needs, necessitated an economy of acquisition, fed the sins of idolatry and avarice, and eroded the common good.

Luther perceived early capitalism as a weapon of mass destruction that exploits the poor and destroys the ethos of community. So he exploded in one of his writings: “The world is one big whorehouse, completely submerged in greed,’’ where “the big thieves hang the little thieves.’’

In somewhat less colorful language, Calvin said the houses of the rich are the slaughterhouses of the poor.

In short, the so-called Protestant ethic is neither Protestant nor ethical.

Carter Lindberg

Northborough

The writer is a professor emeritus at the Boston University School of Theology.