It’s a warm spring Saturday night, and I am standing in a tot lot, knee deep in toddlers. It’s past seven, and the late light is starting to smudge. As I gaze across the garish reds, blues, and yellows of the bulky play structures, across the immovable iron fence, I spot a 20-something couple walking by on the street. They are light on their feet, smiling, arm-in-arm, and I think: They’ve just had sex. A late afternoon session, bodies sweaty, faces flushed, their hair tousled by a post-storm breeze from the window. A prelude on their way to a chic bistro and a boisterous bar. The young man and I trade squinting looks, both trying to make sense of what we see. After a beat, he gives up and rejoins his partner’s earnest banter.

Another thought: I used to be that young man, back before I was a father. It’s like remembering a town you lived in long ago on a street whose name you don’t remember. A shadow life. A theory.

Us and them is the easiest way to talk about this, but not the most accurate. It’s more “us and them-about-to-become us.” Because they will, of course. A 2013 Gallup poll found that only 6% of Americans between the ages of 18-40 say that they don’t have children and never want to have children. It’s all but inevitable. And while some might expect me to say to that father-in-waiting, “Ha! Just you wait! Kiss afternoon sex goodbye,” I don’t. Instead, I think, “Ha! Just you wait! The time you will spend attending innumerable kids’ birthday parties and sitting up nights with a feverish child and changing a hundred thousand diapers and standing in tot lots for hours on end will be the best times of your life.” He can’t know this because for him it’s unfathomable. Until it isn’t.

The orange smudge in the west has become a grey canvas. The young couple is nowhere to be seen. “Daddy!” Norah says, her face and body twisted. “Yes dear?” “I think I have to go poop.” And so we make our exit to a nearby restaurant bathroom—me strolling, Norah tiptoeing in dramatic fashion.

A good day by any measure.