Eastern (Orthodox) church split from Western in 1000 – issues seem pretty trivial:

• whether Eucharist should use leavened or unleavened bread,
• whether the Spirit “proceeds” from God alone, or from father AND son (the Filioque question).

Mostly because Rome tried to impose rules on everyone else. 

Procession of the Holy Spirit

John 15:26 says the Spirit proceeds from the Father, so this is the wording found originally in the Nicene Creed. But the form of the Creed adopted in the West, included “and the Son” (filioque), so called “double procession”.

Most scripture does not really concern itself about whether there is some sort of hierarchy within the Trinity, only that there is a Trinity, and all are equivalent. But people get into who takes what from whom, etc.

Chi-Rho

Chi-Rho symbol (X over a P – first 2 letters of Christ, in Greek) was used by Constantine, first Roman emperor to convert to Christianity. Put it on shields, coins etc. (He was in York with his father when his father died, so it took over 10 years to officially become emperor).

He moved capital to Byzantium and renamed it Constantinople (now Istanbul). 

Icons

Icons (religious images) are not specifically Eastern Orthodox, but there is a continuity of tradition, whereas religious art in the West clearly develops through the Renaissance. Full of symbolism, of course – halos, wings, objects. A visible gospel (especially for the illiterate) and indeed, if worshipped, equivalent to the Son or saint (because otherwise it could be seen as idolatry – and the Orthodox church had its own period of iconoclasm in the 8th centure).

Many were considered to have protective powers, particularly in war. Palladium is the name for such an object (named after Pallas, the image of Athena that protected Troy)!

Usually tempera on wood, with gold leaf. The oldest come from St Catherine’s monastery, in the Sinai. Statues never really took off in the East, as they did in the West.

Crete was a major centre for hundreds of years, while under Venetian control until taken by the Turks. El Greco was influenced by the style, which he took to Venice.

Reformation obviously did it in for icons in the Protestant world.