SIGNS AND WONDERS
As a child believes in Santa Claus, it accepts everything its educators tell him.
Jesus walks on the water, calms the storm with a single gesture, changes water in wine, etcetera.
All these things make a great impression on a child's mind, and help the child believe that God revelead Himself to us in Jesus.
However, although most adults don't take these stories literally, yet they can accept the essence of the Glad Tidings. The bible doesn't lie. It only says what the apostles SAW. A vision is a bit like a dream. Some do see it, but others don't. For example, Saint Bernadette in Lourdes saw virgin Mary, whereas the other children who were with Bernadette saw nothing. This doesn't make the vision of Bernadette less important, because research showed she consistently told the truth about the things she saw and heard, namely that the virgin Mary appeared to her alone and spoke to her. Indeed, a vision is more real than a dream to the extent that God makes something happen outside the phantasy of the perceiver.
Now what remains of the Gospel when we don't take every wonder story literally? More than enough! It's clear Jesus made a great impression with his charisma. By the way he acts he reveals who he is.
"Go back and report to John what you hear and see: the blind receive sight, the lame walk ... and the glad tidings are preached to the poor." (Matthew 11, 4-5)
Catholics believe God can interfere in His own creation in a miraculous way, as He does whenever He creates a living being or even a man. He can push aside the laws of nature. But whenever something miraculous happens, we always have to investigate whether we can explain it in a natural way. Moreover, the evangelists wanted to stress the symbolic sense of the stories.
For a canonisation, the Church demands that three miracles be reported that happened at the intercession of the saint. Mostly, these are miraculous recoveries. Through signs like these, God makes clear that the candidate is in heaven.