Just like anything between two sinful people, friendship can be complicated. Our feelings get hurt. Our expectations aren’t met. We say things we shouldn’t and do things we later regret. But just like anything between two sinful people, friendship is the soil from which grace can abound.

In his great book, The Four Loves, C.S. Lewis said, “Friendship is unnecessary, like philosophy, like art. . . . It has no survival value; rather it is one of those things that gives value to survival.”

We don’t need friendship to live, but who would want to live without it?

Lewis’s words tap into what makes friendship the most grace-full of all relationships. It’s the undeserved joy of life that we can all have. Not all of us will be a mother or a father. Some of us lost our parents long ago. A few of us won’t marry even once in our lives. But we can all have friends. In a very real sense, friendship is the only relational assurance any of us have. There are, in all this world, no friend-less people. I dare you to try to find one.

Lewis is right. We don’t need friends. But his point is just the opposite: we actually do. Friends are the most wonderfully unnecessary necessity.

The thing about friendship is it doesn’t reveal itself as necessary until the right time. Friends don’t go on talking about how great of friends they are—at least not when around one another. They just are together. They talk. They don’t talk. They laugh or they don’t. They see each other when they do and they catch up later if they can.

Friendship is, in a sense, the least demanding of all the relationships. In fact, demanding something from the friendship strains the joy all out of it. No one wants a friend always on your back about being a better friend. The beauty is in the there-ness of it, not the definition of the terms. It’s the thing itself that holds the beauty, and nothing else needs to be said.

The lack of demand is exactly the reason why friendship is the most surprising thing in the world when our world falls to pieces. When life is ripped open and our heart lies raw on the ground, it is friendship that always surprises us. The obligationlessness of friendship makes the presence of friends all the more moving when everything else crumbles. Our family has to be there, but our friends don’t. Blood doesn’t tie them to us nor us to them. Something else does—something no contract defines, no witnesses sign off on, and no vested with power authority must approve.

Julie Beck writes about Friendship for The Atlantic. In a column about two friends named Andy and Gabe, she allows them to tell their story of a weekly high five. In 2014, Andy and Gabe started a tradition once a week where they would walk to the park and give each other a high five. Sometimes they’d stay and talk a while, sometimes they wouldn’t. But they did it once a week for six years. Then Gabe got sick and lost his memory.

Andy tells a story about visiting Gabe in the hospital.

Andy: That first week that he was in the hospital, there was a special high-five moment. He was allowed one visitor a day, and I stayed overnight so his wife could go home and be with their daughter. That night, I asked him, “Do you know who I am?” He’s like, “Yeah. Andy. Did I get that wrong before? I’m sorry.” I asked him if he knew anything about the high five, and he said, “No; what are you talking about?” So I told him the basic story.

The next morning he got up to use the restroom. At that point, his short-term memory was really, really bad, so he wouldn’t have remembered the conversation the night before. I said, “Okay, Gabe, this probably isn’t going to make any sense, but on your way back from the bathroom, I’m going to walk toward you. I need you to give me a high five.” He was like, “Okay.” We did it with his left hand because his right arm had all the IV stuff in it.

I started walking toward him, and then right before the high five, he did the clap, and the snap, and I just started crying. I said, “I can’t believe you just did that.” He was like, “Can’t believe I just did what?” It just blew my mind. I didn’t expect him to remember anything about it.

Gabe: That’s one of the things I love about the routine of it. Not just the mechanics of it, but the friendship part of it is so burned into my body memory that that’s what came out.

High fives turned into tears. Weekly walks turned into a night at the bedside. A memory embedded into the body’s rhythmic habits turned into more than a liturgy. What started so child-like took them to the grown-up shores of the darkest of nights—a place to which only friends can travel. Or, perhaps, a place to which only friends will travel.

It is such moments where the realization dawns upon one or another, if not both, that something more has happened over the course of time. Another friend has been joining the two together for more than high fives. It was, as C.S. Lewis puts it as if the Great Friend himself said, “You have not chosen one another, but I have chosen you for one another.”

Such moments clear the air and make one thing certain if nothing else in life is. Friendship is the most necessary thing in all the world. We can survive without it. But we can’t live.

Author’s Note: I’m indebted to Jonathan Rodgers’s newsletter for drawing my attention to the story of Andy and Gabe.

Editor’s Note: This article was originally published at Things of the Sort.