If A Tree Falls In The Forest And There’s No One Around To Hear It, It Does Not Make A Sound
Most people have heard this question at some point. It has become a sort of cliché of philosophical thinking. It seems like a no-brainer… A tree falls, hits the ground and makes a sound. What does someone being around to hear it, or not, have anything to do with the sound something makes? In some cases, upon hearing this question, people respond with a sneer and prepare to fend off any philosophical mumbo-jumbo. The problem is that the correct and demonstrable answer to this question is no.
In order to understand why no sound is made by the tree we need to first understand what sound exactly is. When asked, most people will explain sound with some description about the objects that generate it and the waves it makes that enter our ears. This common notion about sound mixes two very different things. First, there are the vibrations in the air that are produced by objects like falling trees, loudspeaker membranes and people speaking. Second, there are the sensations we feel when these vibrations in the air move the tympanic membranes and stereocilia (small sensor hairs) inside our inner ears, creating electric signals in our brains.
What we sense as sound is something within our mind. We have a sensation that happens when a note is played on a piano and a different sensation when a champagne bottle is popped. The physical event is translated into something we feel. We naively assume that this sensation is universal and attribute it to the physical event we perceive, but this is not the case. Animals have different sensations that correspond to these stimuli. Dogs and cats have different ears than humans and would have different sensations when a piano key is played or a bottle popped. Bats have extremely advanced hearing and can hear sounds outside the human range. They experience sensations we can not. What does ultrasound sound like? You’d need to ask a bat.
It’s a strange notion but consider that what you hear is quite possibly not what other people hear. Just like there are color blind individuals — people who’s ocular sensors (eyes and visual nerves) generate different sensations than others, it is quite possible for people to perceive sounds in a way that is different. Sound is a sensation, a feeling. It is caused by outside stimulus but it is something internal to our mind and consciousness.
So back to the tree. It causes vibrations in the air — but does it make a sound? The crashing sound of a falling tree is the sensation our brain generates and our mind perceives when certain sound waves hit our ears. And since no one’s ear was there to register the vibrations in the air no sensation of sound was generated in anybody’s mind so there was no sound. The answer is no.
Why did this question become so famous? Why is this important? One of my undergraduate philosophy professors used to say that asking questions about the completely obvious is the essence of philosophy. It is the things we feel are clear and simple that deep philosophical thought seeks to prod and question. Is the world what we think it is? Are we what we think we are? Asking these questions leads to a path of wondrous discovery.
