How do you determine what is and isn't heresy?
Is everything fated...
Has the traditional church i.e. the Church from 33 to 1054 A.D. which compiled the Bible taught it? If no, then it's heresy
What if they condemn something as heresy but is actually sound biblical teaching?
What if you think it is sound biblical teaching but it was actually heretical the entire time?
This is logically contradictory, the Church compiled the Bible, all 46 OT books and the 27 NT books.
The judgement of the apostles vis a vis what gets included in the Bible, is not a different beast from their teaching on other matters, but rather both the Biblical canon and the Church's philosophic thought flows from the same source, Jesus of Nazareth.
Then you go to scripture and give your proof and if you are unable to give biblical backing for it then it is false. As Athanasius says:
(Athanasius, To the Bishops of Egypt, Ch 1, 4)
Jesus of Nazareth is the Rabbi of all believers, so if he didn't preach predestination, there is on reason to believer predestination is not heretical.
**no reason to believe predestination is not heretical.
Sorry, double negative got messed up
If you believe that your church is the true church then why do we see them condemn things that are plainly taught in scripture? Also, you have to understand that your interpretation of patristic texts is also your own personal opinion since there are countless churches that claim apostolicity and depending on your church you can condemn other churches.
He did:
John 17:12
Also, would you deny the Pauline epistles?