Now it becomes faintly interesting. Ponnuru and Robinson both flatly ignore one of the plain and historic meanings of “invincible ignorance” – the extent to which it describes infants, say, or those who could never, for historical or geographical reasons, have been exposed to Catholic doctrine.

Instead they have the nerve to assert that this term covers only those who do not have the moral integrity to accept Vatican teachings. I am well aware of this secondary definition but must confess myself quite amazed at the arrogance of those who invoke it. I am not a Roman Catholic, ergo I am a victim of my want of curiosity or my wilful blindness: in other words of my own “false consciousness.” Satisfyingly circular and fallacious, and ideally designed for serfs on the one hand and cynical priestcraft on the other.

Those to whom this essentially totalitarian idea comes as a surprise might want to look up its rationalisations, which extend as far back as Origen and through Loyola if my memory serves, and were codified by Pius IX in the late seventeenth century. If that is too arduous, the relevant chapter in Mary McCarthy’s “Memoir of a Catholic Girlhood” beautifully illustrates the amorality of the teaching as it was inflicted an inquiring child with an innate moral sense.