Here's a fact that might unsettle you: the cells that make up your body are outnumbered. For every human cell carrying your DNA, there are roughly as many—perhaps more—bacterial cells hitching a ride. You're walking around as a mobile ecosystem, a teeming metropolis of microorganisms wrapped in skin.

This isn't just a quirky biological footnote. It raises genuinely strange questions about identity. If 'you' are mostly bacteria by cell count, where exactly do you end? What makes the boundary of your skin so special? And if your mood, cravings, and even thoughts are influenced by these tiny passengers, who's really running the show?

The human body contains roughly 37 trillion human cells. That sounds like a lot until you learn that bacterial cells in and on your body number somewhere between 38 and 100 trillion. The exact ratio is debated, but the point stands: you are not the majority shareholder in your own body.

Most of these bacteria live in your gut, forming what scientists call your microbiome. They're not invaders or parasites—they're residents, many of whom have been passed down through generations of humans. Your particular bacterial community is as unique as a fingerprint, shaped by your birth, diet, environment, and the people you've touched throughout your life.

Here's where it gets philosophically interesting. We typically think of ourselves as unified individuals—one body, one mind, one 'me.' But the cell count tells a different story. If identity is about physical composition, you're more bacterial colony than human being. Of course, human cells are much larger and contain most of your body's mass. But the numbers still challenge our intuitions about where 'we' begin.

Takeaway

Physical identity isn't as straightforward as ownership. You don't control most of what lives inside you, yet it's undeniably part of what makes you function.

Your bacteria aren't just passive hitchhikers. They're active participants in keeping you alive. They digest food you can't break down yourself, produce vitamins your cells need, train your immune system, and even manufacture neurotransmitters that affect your mood. Without them, you'd struggle to survive.

This creates an odd picture of selfhood. You feel like a singular conscious being making choices, but those choices emerge from a collaboration you never consciously joined. Studies suggest gut bacteria influence food cravings, anxiety levels, and even social behavior. When you 'decide' to eat something, part of that decision may originate from bacterial populations optimizing their own survival.

The philosopher Derek Parfit argued that personal identity is less fixed than we imagine—that what matters isn't some unchanging essence but rather psychological continuity and connection. Your bacterial situation pushes this further. You're not just changing over time; you're a process, a dynamic relationship between human cells and trillions of microbial partners, all somehow producing the unified experience you call 'yourself.'

Takeaway

What feels like individual agency emerges from collaboration. 'You' are not a thing but a process—an ongoing negotiation between countless organisms that happens to feel like a single perspective.

We draw the line at skin. Everything inside the boundary is 'me,' everything outside is 'not-me.' But skin is porous. Bacteria pass in and out. The air in your lungs was just in someone else's. The atoms making up your body today weren't there seven years ago. The boundary is more like a busy border crossing than a wall.

Consider your gut bacteria again. They're inside you, essential to your functioning, and they influence your thoughts and feelings. Are they part of you? If you took antibiotics and wiped them out, would you be less yourself? Many people report feeling different—mood changes, altered digestion, shifts in thinking. Something that was 'you' is now gone.

Perhaps identity isn't about boundaries at all. Maybe 'you' are better understood as a pattern—a particular way of organizing matter and energy that persists through constant flux. The bacteria are part of the pattern. So is the food you'll eat tomorrow, the air you're breathing now, and the people whose microbiomes you swap with when you shake hands or share meals. Selfhood, on this view, is less about containment and more about connection.

Takeaway

The self isn't a container but a pattern. What makes you 'you' isn't the stuff inside your skin but the relationships and processes that maintain your particular form of being.

You are, in a very real sense, a walking contradiction: a unified conscious experience arising from trillions of organisms with their own agendas. This isn't a problem to solve but a mystery to sit with. The boundaries we draw around ourselves are useful fictions, practical lines we sketch for convenience.

Maybe that's the deepest lesson. Identity isn't found by looking inward and finding some pure 'you' untouched by others. It's found in the relationships—with bacteria, with other people, with the world that constantly flows through you.