The filioque (Latin for “and the Son”) is the theological notion that the Holy Spirit proceeds from the Father and the Son, Jesus. This clause is included in the Nicene Creed—seen as a legitimate development—in the Western Catholic Church, but not in the Eastern Orthodox Church, which regards it as a late corruption and heresy. It was not really a matter of controversy until the time of Photius in the second half of the 9th century, but since