What is Life?

It’s an elusive question. Humans have an innate grasp of what is alive and what is not. A cat is alive. A rock is not. It seems simple. Yet, come to put it in words, and it all falls apart.

Something is alive if it breathes, if it moves.

What about plants? Plants are alive, but they do not move.

It’s alive if it exists autonomously.

Inanimate objects exist autonomously too. Consider rocks: maybe their “life” is just simple enough that they do not need to breathe, eat, or move at all to sustain themselves. They just “exist” without external influence; they are autonomous. But they clearly are not alive, right?

It’s alive if it replicates.

A well-equipped 3D printer can replicate itself, does that make it alive?

It’s alive if it’s sustained by biological processes.

In the far future, robots could become advanced enough to be sentient and capable of manufacturing other robots that “live” and interact with each other; despite not being sustained by biological processes, does that not make them alive?

No matter how you put it, some form of “life” will be excluded from the definition, maybe because life is not well-defined after all.

Down at the microscopic level, life as we know it is just a bunch of atoms interacting in unison to display an emergent property which we identify as life. It’s a bunch of atoms that, in the right environment, managed to exist, breathe, move, and replicate, through a limitless set of biological processes. But that’s not the only description of life. It does not make sense to break life down to its basic constintuents, because at that level, nothing is alive. It’s just a bunch of atoms.

I have an idea: I will collect some leaves, tie them together, and wrap them around my body for warmth. I do it. Others see me. They like the idea, and they do the same. Suddenly, everyone’s wearing my plant-based outfit. But people higher up north, they find it useless; they’re still cold. They try adding more leaves, but it doesn’t work. They try using tree bark instead; it works better, but it’s too bulky and slows them down against predators. How are the sheep outside not cold? They shave the sheep and try wearing their clothes. It works! They invent wool-based clothing. Fast-forward a few thousand years, everyone wears clothes, made of all sorts of materials, with all sorts of shapes and colors. People even wear tiny computers on their wrists. The idea of wrapping our bodies with something has proven benefitial, and it has remained with—nay, it has become a staple of—humankind eons later. This idea was born, sustained, replicated, and mutated in and by the human mind. Its survival was supported by the environment in which it existed. It took on a life of its own in the minds of human beings. It was (and still is) alive.

A thing is alive when its continuance is favored by the environment it exists in. It’s a broader application of the process of natural selection. Humans are the ultimate hosts of life. And no, I’m not just talking about the billions of viral and bacterial organisms in and around our bodies. I’m talking about the human mind; it is where ideas are born, where they take a life of their own. And through our communication, ideas spread and replicate, ideas morph, ideas adapt. Ideas live. And in the same sense, anything that can exist, persist, and profilerate is thus alive.

Life is natural selection. Natural selection is life.