"How does one seek union with God?"
"The harder you seek, the more distance you create between Him and you."
"So what does one do about the distance?"
"Understand that it isn’t there."
"Does that mean that God and I are one?"
"Not one. Not two."
"How is that possible?"
"The sun and its light, the ocean and the wave, the singer and his song—not one. Not two."
I'm not sure how literally de Mello intended his vignettes to be read, but I'm not keen on the sun/light and ocean/wave images similes to illustrate the distinction without distance in our relationship with God.
The sun and its light are not one, but they most certainly are two, as anyone who has ever seen the moon at night can attest. The wave is a part of the ocean, or at least the water giving shape to the wave is.
The larger problem, though, is that both similes obscure the implicit equivocation in de Mello's formula, "Not one. Not two." (The singer and his song are also not one, but two, but this simile preserves the equivocation to a much greater extent.)
"Not one" means that, although there is no "distance" between us, God and I are not identical. I am not God; furthermore, (unlike the wave to the ocean) I am not a part of God. (It also means that I am not consubstantial with God, that I cannot say with Jesus, "The Father and I are one," but I don't think that's de Mello's point here.)
I think "Not two," though, properly means that God and I are not additive. The syllogism, "God is one. I am one. Therefore, God plus I are two." is invalid.
And it's not (or not just) that God is infinite, and infinity plus one is infinity. But God and I belong to utterly different orders of being. If I say, "God and I are two," the question is, "Two what?" And there is no "what" that we both are, except by analogy. It would be like saying, "Brer Rabbit and Middle C are two," only more so, since the difference between God and me is greater than the difference between an imaginary folk hero and a musical note.
(This fact, by the way, underscores the infinite and pure grace of Christmas. God is not a man-like spirit who finally got around to creating a body for himself. Rather, he assumed a nature utterly unlike His own (albeit one that is capax Dei, capable of God).)
So I read de Mello's formula as meaning, "God and I are not one being, nor are we two co-measurable beings." Of the three examples he gives, "the singer and his song" comes closest to expressing this distinction.