Editing Pope Sergius III (section)

===Relations with Constantinople===
Sergius, like his predecessors, continued to defend the [[Filioque]] interpolation into the [[Nicene Creed]], which was at odds with the position of the eastern church. Papal legates who attended the [[Synod of Trosle]] in June 909 attacked the [[Greek Orthodox Church|Byzantine]] position, which the synod then condemned in the fourteenth [[Canon law (Catholic Church)|canon]]:
{{blockquote|Sane quia innotuit nobis sancta sedes apostolica adhuc errores blasphemiasque cuiusdam vigere Photii in partibus orientis in spiritum sanctum, quod non a filio, nisi tantum a patre procedat, blasphemantis. Hortamur vestram fraternitatem una mecum, ut secundum admonitionem domni Romanæ sedis præsulis singuli nostrum perspectis patrum catholicorum sententiis de divinæ scripturæ pharetris acutas proferamus sagittas potentis ad confodiendam beluam monstri renascentis et ad conterebrandum caput nequissimi serpentis.}}
{{blockquote|As the Holy Apostolic See has made known to us that the blasphemous errors of a certain [[Photius]] against the [[Holy Ghost]] are still vigorous in the East, errors which teach that the Holy Spirit proceeds not from the Son but from the Father only we exhort you venerable brethren, together with us, in accordance with the admonition of the ruler of the [[Roman See]], after a careful study of the works of the Fathers, to draw from the quiver of Holy Writ arrows sharp enough to slay the monster which is again springing into life.<ref name='Mann 130'>Mann 1910, p. 130</ref>}}
Almost a century later, this decision led to the removal of Sergius's name from the [[Diptych]]s{{clarify|date=May 2025}} by [[Patriarch Sergius II of Constantinople]].<ref>Mann 1910, pp. 130–131</ref>

However, the major issue with [[Constantinople]] that presented itself during Sergius' pontificate was the question over the fourth marriage of the [[Byzantine Emperor]] [[Leo VI the Wise]]. Both the emperor, who wanted to marry [[Zoe Karbonopsina]], and the [[patriarch of Constantinople]], [[Nicholas Mystikos]], appealed to Sergius; the pope sent [[papal legates|legates]] to Constantinople, who confirmed the pope's ruling in favour of the emperor, on the grounds that fourth marriages had not been condemned by the Church as a whole.<ref name='Treadgold'>Treadgold, Warren ''A History of the Byzantine State and Society'' (1997), pg. 468</ref> Nicholas' refusal to accept this ruling saw him deposed by Leo VI, upon which he too appealed to Sergius, claiming his deposition was unjustified.