text: Hey, neither I nor you define "essential part of faith".
  After extensive examination of the individual cases of "apparitions", the Church sometimes (not always) will offer its desired opinion that if you want to believe in these apparitions, then it is not against Catholic belief.
  That means you can be fully Catholic and not believe in the Lourdes apparitions, the Fatima apparitions ...
  For all that precedes, I am merely stating facts. 
  
  (Total transparency: I have been to Lourdes three times, and to Faitma once.)