There’s a moving scene in “Our Town,” Thornton Wilder’s classic play about small-town America, in which a doctor’s wife named Julia Gibbs openly worries about her young son, George, on his wedding day.

Julia was young once, too, and she knows all too well that on her long-ago trip to the altar, she had no real idea what her love for her husband would give her — and what it would also demand of her. She wants George to know about what he’s getting into from the start.

But love doesn’t reveal its implications all at once, and it never fully discloses the secrets of its workings. There is a mystery about it that can’t be neatly explained or summarized — not by a congress of poets, by a convention of scientists, by a host of theologians or by all of the Valentine’s Days on the calendar.

Even so, we never stop trying to explain love, as the arrival of another Valentine’s Day reminds us.

The commerce of Christmas inspires complaints each December that all of our holiday shopping has essentially reduced something sacred to a business transaction. There are now similar anxieties about Valentine’s — that the holiday’s candy, designer pajamas and candlelit meals might be commodifying connections that should be about the spiritual, not the material.

We understand those concerns, although perhaps there are worse evils in the world than taking someone you love to dinner or giving your sweetheart some chocolate or buying that special person some sleepwear a bit more provocative than standard-issue winter flannel.

We’ve noticed that painful word, “evil,” has just slipped into our reflections here, if only because the darker impulses of our species tend to shadow our national life these days.

The headlines this winter give us pause. Beheadings and burnings can make even the sunniest optimist wonder if hate has gotten the upper hand on love.

But Valentine’s Day takes its name from a Christian martyr of long ago, a reference that reminds us of the enduring presence of suffering in human affairs.

Valentine’s Day tells us, though, that love endures, too. That’s the point of Wilder’s “Our Town,” really. Not much happens in the play’s fictional community of Grover’s Corners — at least nothing that would make news or inspire a reality TV show. What happens, essentially, is that many people wake up each day and try their best to love those close to them, a fidelity that’s persisted in every corner of the Earth, in places large and small, throughout the tattered pageant of existence.

Love grows so deeply and widely, and against such long odds, that it’s easy to take it for granted.

Valentine’s is a day to remember, with joy and passion, the great capacity of the human heart.