The filioque.  It’s still used by anti-Western Orthodox as the number one cause for the schism.  As I stated before, however, the underlying issue that still separates is the role of the papacy.

I am really, really busy with planning for an RCIA class and work, so I’ll leave you with some preliminary reading before I weigh in on the topic.

The Spirit and the Filioque Debate (Pope John Paul II)

The Filioque: a Church-Dividing Issue? An Agreed statement of the North American Orthodox-Catholic Theological Consultation