But it was an “open canon” which allowed them to add the books they did.. an “open canon is in reality no canon
In that case the RC charge that there was no canon until Rome provided it would be true, though under that definition of canon that would mean that for most of her claimed history then she had none.
Moreover, it is actually a discussed but unsettled matter among RCs (http://forums.catholic.com/showthread.php?t=654381; http://forums.catholic.com/showthread.php?t=677608) as to whether Trent actually closed the canon, versus settling that the listed books are Scripture, but not saying other books are not. The Eastern Orthodox Churches were using a larger canon before Trent (including the Prayer of Manasseh) but Trent did not condemn such usage. And as the above forums state the RC apologist Gary Michuta reports that the Council took up the issue as to whether certain books (the Book of Esdras, Fourth Ezra, and Third Maccabees) that were included in [some of] the Latin Vulgates should be rejected by a Conciliar decree, or be passed over in silence. He reports that only three Fathers voted for an explicit rejection, while forty-two voted that the status of these books should be passed over in silence.
But the word "canon" does not necessarily mean a complete list of books, but can refer to "a sanctioned or accepted group or body of related works," (http://www.merriam-webster.com/dictionary/canon) as a canon of great literature.
And which certainly existed in the time of Christ, otherwise He could not have challenged the Jews to "search the Scriptures," as that presuposes a body of accepted writings being Scripture, and the Lord preached from to the disciples,
"which were written in the law of Moses, and in the prophets, and in the psalms, concerning me. (Luke 24:44) and likewise which Paul "expounded and testified the kingdom of God, persuading them concerning Jesus, both out of the law of Moses, and out of the prophets, from morning till evening." (Acts 28:23) And for Paul at least, the Law could include Psalms and Proverbs and prophets.