In this task you will be given an answer to a question. You need to generate a question. The answer given should be a correct answer for the generated question.
Q: This doctrine was defined dogmatically at the First Ecumenical Council of the Vatican of 1869 -- 1870, but had been defended before that, existing already in medieval theology and being the majority opinion at the time of the Counter-Reformation.
A: 
when did the doctrine of papal infallibility begin