A significant point of theological divergence arose with the addition of the Filioque clause ("and the Son") to the Nicene Creed in the West. While the Orthodox position is that the Holy Spirit proceeds from the Father through the Son, the Western addition states that the Holy Spirit proceeds from the Father and the Son.

This clause was officially added to the Latin Nicene Creed in Spain during the sixth century and was later promoted by figures like Charlemagne in the ninth century as a distinguishing factor between the West and the East.

The Western addition was partly motivated by a desire to combat Arianism by asserting the co-equality of the Son with the Father. However, the Orthodox tradition explicitly condemns the Filioque. The critique is multi-faceted:

The change was made to the Creed without the right to do so.

The Filioque disrupted the relationally and structure of the Holy Trinity. If the Father and the Son together act in the Holy Spirit, it diminishes the unique role of the Father as the sole origin and affecting the distinct relations between the persons.

The differing understandings of the Essence Energy Distinction in the West are also seen as contributing to their different approach to personhood theology compared to the East.

Prominent figures who explicitly condemned the Filioque in the Orthodox tradition include Saint Photius the Great, Saint Mark, Bishop of Ephesus, and Saint Gregory Palamas. The writings of St Gregory Palamas on the procession of the Holy Spirit, particularly his emphasis on the energy-essence distinction and personhood theology, are hugely important in this discussion.