I can't define it, but I know it when I see it.
That's the famous paraphrase of U.S. Supreme Court Justice Potter Stewart's 1964 attempt to define obscenity.
It's what came to mind when I started thinking about information.
Most of us never stop to ask what information actually is. We take it so much for granted because it surrounds us constantly. It is so pervasive, and appears in so many different forms, that defining it is far more difficult than it first seems.
There is written and spoken information, conveyed through language and symbols. There is biological information, encoded chemically within living cells and passed from one generation to the next. There is computational information, represented by the ones and zeros of digital computers, and at an even smaller scale, by the qubits of quantum computing.
What could these seemingly different things possibly have in common?
The clue may lie hidden in the word itself. Information in-forms. It gives form within. Once received, it reshapes us. It influences what we know, how we think, what we perceive, what we feel, and ultimately how we understand and act upon the world.
Perhaps information cannot be defined by what it is made of any more than music can be defined by the material of the instruments that produce it. Music is not wood, brass or vibrating strings; it is a pattern expressed through them. Likewise, information is not ink, sound waves, electrical impulses or molecules. These are merely the media through which it travels. Information is better understood by what it does than by what it is made of.
It can be transmitted, stored, received, transformed, interpreted, encoded, compressed and copied. Yet none of those properties quite captures its essence.
I'm hardly the first person to wrestle with the question. Scholars have debated the nature of information for decades across mathematics, computer science, physics, biology, psychology, philosophy and many other disciplines. The subject has become so influential that some regard Information Theory as one of the defining intellectual achievements of the modern age.
Yet information does not require consciousness. Plants process information. Immune systems process information. Even a thermostat responds to information. As anthropologist Gregory Bateson famously suggested, information may simply be "a difference capable of making a difference."
That insight points toward something deeper. Information is not defined by the material that carries it, but by its capacity to produce change. Data becomes information only when it informs—when it alters the state of whatever receives it. It may teach us something new, confirm a suspicion, correct a misunderstanding, trigger a response, or reveal a pattern that was previously invisible. Therefore, information is less a thing than an event: the act of one system changing another.
Similarly, thinkers are also still grappling with a definition of life itself. Is it a 'thing' or a 'process'? Maybe life itself is nothing more—or less—than the continual gathering, interpreting and acting upon information. Every living organism survives by sensing differences in its environment and responding to them.
What about computers? They gather, store and process information too. Does that make them alive? Of course not. Computers manipulate symbols according to formal rules, but the symbols have no intrinsic meaning for the machine itself. The computer's internal state changes, but nothing is 'understood'.
Data (stored as a pattern of ones and zeros, for example) has no meaning. Meaning is what information provides.
Which brings us back to Justice Stewart.
"I know it when I see it."
He wasn't really offering a definition. He was describing a transformation. Seeing something altered the state of his understanding.
Perhaps that is the closest we can come to defining information. It is whatever has the capacity to make a meaningful difference in the recipient. The means of conveyance doesn't matter. The material it's made from doesn't matter. All that matters is that it leaves us differently formed than we were before we encountered it. It's the receiver, the viewer, the perceiver, the mind, that determines whether it's information not the transmitter.
That means anything can be information, or not.
We may have arrived at a definition of consciousness as the process of turning data into information, and information into awareness.