In "A Brief Apology of St. Gennadius Scholarius," the author critiques the Latin Church's addition to the Nicene Creed, particularly the "Filioque" clause, which he argues is a significant theological error that led to the schism between the Eastern and Western Churches. He asserts that the Latins acted unilaterally and without the consensus of the broader Church, undermining their authority. Gennadius defends the Eastern Church's position, highlighting the historical fidelity to the original teachings and the importance of adhering to the decisions of the Ecumenical Councils. He concludes that unity cannot be achieved without the removal of the contentious addition.