Are there dogmas in the Orthodox Church? What are the dogmas and the things that are opinions?
Yes, Orthodox Christianity has dogmas; however, to truly appreciate what that means, one must understand what the word “dogma” refers to. In our modern era (especially in the United States) the words “dogma” and “dogmatic” have negative connotations — they refer to those who cannot or will not change their position, despite overwhelming evidence to the contrary (the belief that world is flat, for example.) Though it is true that dogmas do not change, this is not a bad thing. In fact, it is a very good thing.
Dogmas are the various summary statements about revelation that have been received by Orthodox Christianity throughout the centuries. For example: The Nicene Creed. In other words, dogma is about God and Salvation. Even the dogmatic title given to the Virgin Mary — Theotokos (birth-giver of God) — speaks about the Word of God and His Incarnation.
Since God does not change, dogma does not change. Orthodox Christians, through the bishops and council, may make new statements to deal with changing contexts, but these statements do not and cannot change “the faith once and for all delivered to the saints” (Jude 3) or who God is; it is only our understanding of revelation what should brighter as we strive to be “witnesses to the truth.”
Dogmas are (1) based in the revelation of the Holy Scriptures (2) have been confirmed by the Ecumenical Councils.
Opinions (technically called “theologoumenon”) are those things that do not directly affect our understanding of who God is and for which there is not clear Scriptural teaching.
An example of this is the Orthodox position on the Assumption of Mary*. While this belief is popularly held by many Orthodox Christians, it is not necessary to accept it in order to be an Orthodox Christian. The same cannot be said about the Orthodox Christian teachings found in the Nicene Creed or the teachings of the other Ecumenical Councils regarding the the divinity and humanity of Christ our Savior.