Article 4

Books of the same authors which do not expressly treat religion, but only incidentally touch truths of faith, are not to be held prohibited by ecclesiastical law until they have been proscribed by special decree.

Proper force of the article

68. Therefore, even if certain religious truths are denied, provided they do not defend heresy or schism nor overturn the foundations of religion (art. 2), these books, if only incidentally or as if accidentally they touch truths of faith, are not prohibited by general decree. And although it can happen that by the natural law they are forbidden at least to certain persons, ecclesiastical law passes them over until a special decree has appeared.

This milder discipline had already prevailed by usage in several places.