We believe that the visions of Mary that have occurred in Lourdes, France, Medjugorje, Yugoslavia, and many other places, can be evaluated on the basis of scriptural, factual, and psychological evidence.
Bernadette Soubirous, the young adolescent girl who had a series of visions of Mary at Lourdes, convinced thousands of people of her sincerity. On one occasion, several thousand people observed her as she spoke with an invisible visitor that only she was able to see. There is little reason to doubt that she actually did see what she considered a vision of Mary. But did she really see Mary, or an illusion created by her imagination and projected by her subconscious mind?
Consider how differently Christ appeared to His disciples following His resurrection. He wasn't invisible to some as He spoke to others. Jesus had a solid physical body, actually challenging Thomas to touch Him on one occasion and eating fish with the disciples on another( John 20:26-29 ; Luke 24:36-43 ). He never appeared as an "apparition" that could be seen only by a select few.