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First of all, does the Orthodox teach that these books ARE scripture? Or are they just good, useful, supplementary books that are still acceptable to read in the liturgy? What I've gathered so far is that the answer is the latter, but I just wanted to confirm since Ive heard different things.
There is a range of opinions on this. From what I can tell they are generally considered Scripture, but some would put them "on a lower footing," while a select few would question their canonical status entirely. The thing about it is, since the Orthodox Church is not so reliant on Scripture as the end-all, be-all for establishing doctrine, this isn't as big a deal as it would be for some other groups. Also, this leaves the Orthodox in basically the same boat that the early Church was in: and not having a dogmatically-settled canon in the early Church certainly didn't seem to keep them from practicing the Christian faith. Here are what two modern Orthodox writers say about this:
"The Orthodox Bible contains certain other Scriptures besides that normally found in the Hebrew bible and most English language Bibles. The word Apocrypha means things that are hidden, although why so is not positively known. Sometimes these books are given the title Deutero-canonicalas contrasted to Proto-canonical to distinguish the first (or proto) canonical books from those that came later (deutero—second). This term is to be preferred over Apocrypha since that word may have negative meanings. The Deutero-canonical books appeared as part of Holy Scripture with the translation of the Hebrew Scripture into Greek by Alexandrian Jews who had been gathered together for that purpose in Egypt just prior to the New Testament times. Over the centuries, however, these books have been disputed by many; many hold them to have little or no value as Scripture. However, both the Orthodox and Roman Catholics accept them as part of the Biblical Canon, whereas, since the Reformation, most Protestants have rejected them as being spurious. Although the Orthodox Church accepts these books as being canonical, and treasures them and uses them liturgically, she does not use them as primary sources in the definition of her dogmas." - A Monk of Saint Tikhon's Monastery, "These Truths We Hold," The Holy Orthodox Church: Her Life and Teaching
"The [Orthodox] Church accepts these latter books also as useful and instructive and in antiquity assigned them for instructive reading not only in homes but also in churches, which is why they have been called 'ecclesiastical.' The Church includes these books in a single volume of the Bible together with the canonical books. As a source of the teaching of the faith, the Church puts them in a secondary place and looks on them as an appendix to the canonical books. Certain of them are so close in merit to the divinely inspired books that, for example, in the eighty-fifth Apostolic Canon, the three books of Maccabees and the book of Joshua the son of Sirach are numbered together with the canonical books, and, concerning all of them together, it is said that they are 'venerable and holy.' However, this means only that they were respected in the ancient Church; but a distinction between the canonical and non-canonical books of the Old Testament has always been maintained in the Church." - Fr. Michael Pomazansky, Orthodox Dogmatic Theology
Second: I understand the Septuagint was a Greek translation of the Hebrew OT. It was being translated during the 300 years before Christ was born. Was the apocrypha part of the original Hebrew? .... etc....
Many of the deuterocanonical books were written in the 2nd century BCE, and didn't gain widespread acceptance among the Jews as being worthy of inclusion in their canon (even though they were still discussing the boundaries of their canon centuries later). When it came to which books were sacred Scipture, things were really quite foggy in those days, for both Christians and Jews.