‘Finger pointing at the moon’ is a Zen koan, which means it is impossible to say what is. If I say the word "apple," it doesn't really mean an apple. It could signify the apple I left in the refrigerator. That could be useful temporarily, but it doesn't have any ultimate meaning in terms of "apple": it's only a symbol to represent something.
Even if Shakyamuni Buddha himself were to come to us, the teaching that he would give would not be the ultimate truth. The truth cannot be told. Words are just sounds; they have no ultimate meaning. The Dharma with a capital "D" is just another one of dharmas (phenomena). It is fabricated; it's a part of the skandhas. The skandhas of your mental body, emotional body and physical body need to align within the wisdom of Dharma, which means we become enlightened through not knowing. This is not to imply we don't need to receive teachings, but rather that all teachings aren’t true.
What spiritual teachings are supposed to be is pointing to the moon. I'm pointing because I want you to know about the moon. I can't really give you the moon because it is already there in the sky. Everything I do is simply pointing at that moon over and over again. You may hear me saying different things, but each one is another way of pointing at the moon. Sometimes I point with my hand straight up in the air; other times I gesture with my index finger. I might jerk my arm back and forth, jump up and down, or even run in circles and shout, "Hey, look up there!” In various ways I’m trying to get you to see the moon.
Some people refuse to gaze at the moon. Those who aren’t able to look up, whose necks are bent down, are like animals. They only can look down; they can't look up. What the masters and bodhisattvas do for these folks is tell them stories about the moon. They give secondary teachings to people of lower intelligence so that in the future they can be in resonance with the kingdom of heaven.
If spiritual teachings can only point at the moon, what allows some people to recognize their nature upon receiving those teachings?
What makes them recognize their nature is they understand what pointing at the moon means. We could drink some wine, eat a cracker and take Communion; we could get dunked in the Jordan River and receive Baptism; or we could point at the moon and say, "That's the moon up there. See my finger? I'm pointing at it. There it is." Most people don't believe the moon is there because they have nihilism, that is, pessimism or fear. Then they flip to the opposite and have immature hope. Hope and fear are not it.
What is being pointed at in the Communion, the Baptism, or pointing to the moon is something transcendent: how things actually are. Some people understand what is being pointed at. We can do a little dance or perform a ritual, but we can't really say what is. The symbol is only a metaphor, a substitute. We dunk someone in a river or sprinkle water on them because water is flowing and cleansing; it’s a very magical substance. The moon is a mystical, glowing orb in the sky, and we point at it. Of course, we are not really pointing to the moon. We are not astronomers; the moon is merely symbolic. My finger indicates, "Look at that!" A person who didn't understand would think, "There must be something very esoteric about the moon." No, it's not just about the moon. There is a finger—pointing to—the moon.
The question is why does one person not get it and another person get it? The answer is the person who doesn't get it is obscured, and the person who gets it is unobscured. The first person does many conceptual somersaults and proclaims, "The moon's rays are healing me and I'm having a visionary experience!" but that isn't really what is happening. The second person has a clear, non-manipulative mind. They realize that the thing to “get” is something intrinsic, and they recognize the siddhi and have the samadhi of suchness that arises from that. Their mind is like water, which can take any imprint or shape.
Finger pointing at the moon, water Baptism, wine and bread Communion are all symbols for recognizing one's nature.