text: Newman supports me as I've shown above and that is good enough for me. 
  If the Magisterium can err then the Church has no authority to teach. The Church, however, received the authority to teach from Christ, Himself: Christ cannot err, therefore His Church cannot err.
  The old chestnut about slavery is easily disposed of. Did Christ tolerate slavery? No. It was part of the fabric of society in those days and there is no doubt that there were very many abuses of the system. 
  Similarly the medieval Feudal System incorporated many abuses. Both systems probably allowed millions to survive and live relatively comfortable lives who would have otherwise died very early in life in abject poverty.
  Our modus vivendi today is far from perfect so it is hypocritical for us to stand in judgement on our ancestors.