Question: As the Pharisees were to be heeded because they spoke from Moses’ chair - so also the Pope must be heeded when he speaks from the chair of Peter (ex cathedra).
Answer: Our Lord Jesus instructed His disciples that 'the scribes and the Pharisees sit in Moses’ seat. Therefore whatever they tell you to observe, that observe and do, but do not do according to their works; for they say, and do not do' (Matthew 23:2,3). There is a sense in which the Pharisees were "successors" of Moses because their job was to teach and proclaim the Mosaic Law. As long as they were faithful to Moses' teaching, the people should obey them even though the teachers' lives were inconsistent with their teaching.
But does that mean that they were infallible, simply because they spoke 'ex cathedra'? Most certainly not! Indeed the scribes and the Pharisees were the leaders of Israel who rejected their Messiah, the Prophet about whom Moses spoke. They should have lead the people to Christ; instead they lead Christ to be crucified!
They abused their position of responsibility; therefore they forfeited their privilege and authority. From then on it was the duty of God's people to disregard the scribes and Pharisees, reject their false teaching, leave their synagogues and join the sect of the Nazarene. In so doing, these early disciples were following Christ who had previously warned them to beware of the doctrine of the Pharisees and of the Sadducees (Matthew 16:12).
Similarly, the bishops (also known as pastors and elders) in the various churches in the post-apostolic age should proclaim the teaching of the prophets and the apostles, while God's people should respect them and heed their teaching. But when if some bishops contradict the apostolic message (like their predecessors had done before), then it becomes the duty of all Christians to reject them and regard them as apostates.
That is exactly what happened in history. The present so-called bishop of Rome and his fellow bishops who teach a false and distorted gospel are apostates. Woe unto them who follow them. Beware of the doctrinal leaven of them who sit ex cathedra in the name of the apostles when in reality they teach their own traditions.
Christ has His faithful servants today who speak authoritatively because they are devoted to the apostolic Faith recorded for certain in the Holy Bible. They are the pastors in evangelical churches who preach the gospel of salvation by grace through faith in Christ and not of human works.
© Dr Joseph Mizzi