While reading Charles Sanders Peirce recently, I came across one of his sweeping statements:

“The universe is perfused with signs, if it is not composed exclusively of signs.”

Peirce believed that signs aren’t limited to language. Smoke can signify fire. Tree rings signify age. A thermometer reading signifies temperature. For Peirce, sign processes are woven throughout reality.

That idea reminded me of an old philosophical puzzle: if a tree falls in the forest and no one’s there to hear it, does it make a sound?

Physically, of course, the falling tree produces pressure waves in the air. But if no creature hears the sound, the event never becomes part of anyone’s experience.

Reading Peirce suggested a slightly different way to frame the problem.

When the tree falls, the sound waves exist whether anyone hears them or not. In Peirce’s terms, a sign involves more than a physical signal. A sign stands in a relation that allows it to be interpreted—what Peirce called an interpretant.

So the falling tree produces a signal that could become a sign, but only if some interpreter encounters it.

That made me think of Schrödinger’s famous cat thought experiment. In quantum mechanics, the cat in the box is described as being both alive and dead until observation resolves the situation.

A falling tree without a listener isn’t quite the same, but the analogy is tempting. The sound waves exist, but their status as a sign remains unresolved until some organism or instrument interprets them.

In that sense, the falling tree produces what might be called a Schrödinger’s-cat sign: a signal that both is and is not functioning as a sign, depending on whether interpretation occurs.

Peirce would probably object to the quantum metaphor. For him, the sign relation exists as a potential even if no one happens to interpret it. The falling tree produces a phenomenon that could signify something to an interpreter.

But the thought experiment still illustrates an interesting point: Meaning isn’t located entirely in the world, nor entirely in the mind. It emerges from the interaction between events and interpreters.

The universe may indeed be perfused with signs. But without interpretation, signals remain only unregistered noise.