How do we know with certainty which of the Church councils are valid and which are not?
Catholics accept 21 councils, but reject the Second Council of Ephesus (the “Robber Council”).
The Orthodox and many Protestants accept seven of the first eight (also rejecting the Robber Council).
The Oriental Orthodox accept the first four. Others only the first two or three.
So, what are the criteria for determining which councils are to be accepted and which are not?
And specifically, why do you reject any particular council or group of councils from the list?