Getting a tattoo may be a way for your past self to dominate your present self, but getting sick of your tattoo is a way for your present self to betray your past. That’s what makes the ubiquity of tattoos among Americans my age so unsettling: When we all got them together, they became a symbol of youth, which is a substantially less fun symbol to have around when you are old.

Students of Jean-Paul Sartre will recognize here the problem of existential anguish, which he explains in “Being and Nothingness” through the metaphor of vertigo. The sense of vertigo you feel when walking along a narrow mountain path, Sartre writes, is not the fear that you will fall off but rather the fear that you will suddenly decide to jump. Free will is terrifying because it necessarily entails the freedom to change radically in the future.

The freedom to do anything we want later becomes the freedom to thwart our present desires. I decide to quit smoking now, but later, when someone offers me a Lucky Strike, I exercise my free will to decide that what I really want to do is quit smoking tomorrow. Halfway to the filter, I realize that actually I wanted to quit all along, and the question of who is in charge becomes depressingly complicated.

The tattoo tries to make an end run around this problem by indelibly marking the one part of the self that remains tangible and consistent: the body. It is what behavioral economists call a precommitment device, ensuring that our present values remain in force in the future. You take a cab to the bar when you are sober, so that you will not be tempted to drive home when you are drunk. You wish to stop texting your ex-girlfriend late at night, so in the clear light of morning you delete her number from your phone.

“Asterisks are cool,” Past Dan says. “I will tattoo an asterisk on my body, so that people will see I am an exception to something and I will remain cool forever.” The problem with this is that tattoos are symbols, and their meanings change with context. “Oh, right,” Present Dan says when he catches his asterisk in the mirror during yoga. “I used to be a jerk.”

The tattoo starts as an assertion of your freedom — in, say, 1998 — and lives on as an abridgment of it. When I was 19, I could do whatever I wanted, and the thing I wanted to do was mark my body permanently so that I couldn’t change what I wanted in the future.

In this light, we can read my generation’s mania for tattoos in two ways. We might take it as an expression of ignorance. According to this reading, I and my fellow college students got tattoos because we could not conceive of a time when we wouldn’t want to have drawings of barbed wire on our biceps, which is exactly the kind of hubris that characterizes youth. That’s a plausible explanation, but it’s also cynical. And cynicism is exactly what a tattoo denies: It asserts that some values, be they Pink Floyd or three dolphins that represent infinity, are eternal and unchanging. Perhaps my asterisk is not a dumb expression of my youthful fatuousness, but a wise precaution I took against unreliable middle age.