The boy reached through to the Soul of the World, and saw that it was part of the Soul of God. And he saw that the Soul of God was his own soul. And that he, a boy, could perform miracles.
The believers in miracles accept them (rightly or wrongly) because they have evidence for them. The disbelievers in miracles deny them (rightly or wrongly) because they have a doctrine against them.
A blade of grass is a commonplace on Earth; it would be a miracle on Mars. Our descendants on Mars will know the value of a patch of green. And if a blade of grass is priceless, what is the value of a human being?
The genuine realist, if he is an unbeliever, will always find strength and ability to disbelieve in the miraculous, and if he is confronted with a miracle as an irrefutable fact he would rather disbelieve his own senses than admit the miraculous also.
There is nothing that God hath established in a constant course of nature, and which therefore is done every day, but would seem a Miracle, and exercise our admiration, if it were done but once.