With thanks and apologies to Eliezer Yudkowsky.
We've all heard this argument before. The argument
is a mistake. Even cognitive scientists sometimes make this mistake, and they should know better.
If a tree falls in the forest and no one hears it, does it make a sound?
Armando: Of course it does! I've heard trees fall before, there was quite a lot of sound. It's not like the world behaves differently when people aren't around to observe it.
Dippet: Hold on. How can it be a sound if no one hears it?
In this example, the dispute begins over a genuine difference in their intuitions about what constitutes "sound". There are other ways it can start. Dippet might have a motive for rejective Armando's concluson. Perhaps Dippet is a sceptic who immediately, even reflexively, scrutinised Armando's argument for logical flaws, and when he found a counter-argument, automatically and immediately accepted it without scrutinising
that argument, arguing himself into the opposing position. Which may mean that Dippet may have taken the same position as Armando if he had answered first.
Armando: No sound? What? Roots snap, branches rustle, trunk falls and hits the ground. The impact generates vibrations in the ground which propagate through it and the air. The energy of the fall goes into sound and heat in the atmosphere. Are you suggesting, sir, that when people are not around to keep an eye, or, ha ha, an ear on forests they violate conservation of energy?
Dippet: No, that's all true, but no one hears it! If there are no people or anything else with a complex nervous system and auditory inputs, then no one hears any sound at all. No sound!
Both characters have recruited arguments that
feel like support for their positions. For Armando, the mechanical properties of acoustic vibrations in the air activate all the points in his neural network that indicate "sound". For Dippet, the experience, the "
quale" of auditory experience is what his mind accounts for as "sound". Notice that neither Armando nor Dippet disagree with what actually happens in the forest. The wiser among you will have already identified the mistake that both have made in starting this argument.
Armando: By the Power of Greyskull, this argument is dumb. And you're a stubborn shisno.
Dippet: Shut up, you Prince of Wales.
Not technically part of the argument, insofar as rationalists will record it, but insults are common enough to mention. Neither side can possibly back down now.
Armando: a falling tree produces acoustic vibrations. By definition there is sound.
Dippet: No one hears anything. By definition there is no sound.
They start wielding definitions like they were knock-down arguments (and you just know that a dictionary reference is looming). We've all felt tempted to use arguments like "by definition" in the past, even when what we're talking about is not
pure mathematics. Anything that is true "by definition" must be true in all possible worlds, and if used correctly such arguments do not constrain
which world it is that you live in, or are talking about, and as you know, an explanation that can account all imaginable possibilities explains absolutely nothing.
When used incorrectly, of course, it is all bollocks anyway.
Armando: I can use my compueter's microphone to record a sound that nobody was around to hear. It is saved as a "sound file". It is a record of a pattern of vibrations in the air, not the neural impulses of someone's brain. "Sound". Means. Vibrations.
The argument has devolved into one about what particular meaning the word "sound" is supposed to have. Which is progress of a kind, I suppose.
Dippet: Does it, well, let us see what Mr Dictionary has to say on the issue...
And there it is! Even with advance knowledge of how this fictitious conversation would go, I was hoping they would not resort to the dictionary. They
could have gone to a forest to study trees, particularly logging sites. They might have opened a physics textbook to learn how to derive the wave equation for air pressure changes, researched the anatomy of the ear, examined the neurology of the auditory cortex.
But they'd rather consult the dictionary to arbitrate their discussion. Were the editors expert physicists? Neurologists?
Botanists? Possible, but unlikely. An encyclopaedia, maybe, but a compendium of words and meanings is useless to Armando and Dippet.
Armando: Aha! And what do we have here? Definition 2c in Merriam-Webster: 'Sound: Mechanical radiant energy that is transmitted by longitudinal pressure waves in a material medium (as air).' Well, that about wraps that up, I think.
Dippet: No no, look here: Definition 2b: 'Sound: The sensation perceived by the sense of hearing.'
...
Armando and Dippet: CURSE YOU MERRIAM-WEBSTER!
It is often forgotten that dictionary editors do not legislate the proper use of language, they are historians that record the common use of it.
Armando: I can record the very real acoustics of a tree falling in an abandoned forest and play it back to anyone. That is sound! That is the common usage!
Dippet: You don't get to define what is common usage. I can define a word as whatever I what if I use it consistently. Desides, my usage is actually in the dictionary already.
Armando: Argh! This is the end of language!
Agreeing with everything that goes on in both the forest and the brain does not generate any feeling of agreement. Arguing about definitions is quite the garden path, one that would go untrodden if everyone could see where it leads. "That cur trying to redefine the word 'sound' to support his ridiculous argument!" is what both of them could say.
In an alternate reality born of this one due to outside interference...
If a tree falls in the forest, does it-
Lightning crackles in the air. A glowing sphere flashes into existance, then grows to two metres in diameter. Fading, a man is revealed. Enter Joe Doubtfire. Stray forks of lightning crack this way and that as the energy fluctuations die, and Joe Doubtfire steps forward from the charred circle of ground. His skin is pale and translucent, through which a criss-crossing of dark pulsing vessels is visible. His right arm is entirely mechanical, is left eye glows red with unnatural light, his legs are supported and blended with artificial constructs. Thick black tubes emerge from his torso and bury themselves into the side of his skull, and his armoured chest is emblazoned with the image of a wincing owl. Truly this traveller's origins are dark indeed
Joe Doubtfire: I come to thee from the future. Take heed of my words!
Dippet: Holy shit!
Joe: Should the word "sound" be defined to include both acoustic vibrations in the air and the quale of auditory experience, just the acoustic vibrations or just the auditory experience?
Armando: What?
Joe: Armando, is it? Yes, your brain was not retained by the Overberg, only your hands were granted a place in the New Order. Answer, or face a fate worse than you can imagine.
Armado: Erm... well it wouldn't really matter, I suppose, so long as it was used that way consistently.
Joe: The first Decree of the Overberg ruled should this issue arise, both parties should switch to using unambiguous low-level constituents, such as "acoustic vibrations" or "auditory experience". Or even designate a new word for each for those purposes. "Hubdrub" for the former and "Hemtuft" for the latter, for example. Both sides must use the words consistently of course, so that they don't have to back down but are still able to communicate. They should also keep track of some testable proposition that the argument is actually about. This was one of the few reasonable Decrees, before the dark times set in. How does that sound to you two?
Armando: Fine, I guess...
Dippet: Why...?
Joe: Some years from now the idiocy of this and similar irrational ways of thinking caused a madman... an old friend, to lose his humanity. The horrors he inflicted on us, to raise the human species to a state of perfect rationality in some mad effort to make up for the rapid loss of his own... they are indescribable. You see what has become of my flesh. But that is a contingency you will never know. The future has already been changed!
A bright flash. Exit Joe Doubtfire.
Armando: My god. Er, what were we talking about?
Dippet: If a tree falls in the forest and no one hears it, does it make a sound?
Armando: Ah, well, it makes a Hubdrub but not a Hemtuft, does it not?
Dippet: Agreed, old friend.
