Yes, he's referring to ignorance of the minimal truths necessary to be known in order for there to be salvation, which are belief in the Holy Trinity and Incarnation.
For 1500 years, the Church taught and every Catholic without exception believed that knowledge of the Holy Trinity and Incarnation (basic knowledge about Our Lord and the Holy Trinity) were necessary for salvation. But a Franciscan and some Jesuits came along and invented "Rewarder God" theory, where you just had to believe that there is a God who rewards the good and punishes the wicked. This was developed for emotional reasons after the discovery of the New World, the Americas.
I love it how the majority of BoDers claim that we must accept a consensus of theologians for about 400 years as definitive of Catholic dogma, but then think it was OK and permissible for these guys to come along and reject 1500 years of unanimous, unquestioned Catholic teaching. They'll cite St. Thomas as an authority on BoD but then ignore St. Thomas when he too teaches explicit knowledge of Our Lord and the Holy Trinity are necessary for salvation.