down to earth

7 March 2006 at 12:44 (General)

“Colors, tones, smells, and tastes are mental creations constructed by the brain out of sensory experience. They do not exist as such, outside the brain. Thus we can now answer the old riddle: Does a falling tree make a sound if no one is near enough to hear it? Sound, as we know it, occurs only when pressure waves from the falling tree are perceived by the brain of a living being.”

‘Principles of Neural Science’, by Kandel, Schwartz and Jessell. (4th edition, McGraw Hill)



  1. Kent said,

    Does the tree make a noise if it falls over next to a tape recorder?

  2. toto said,

    I was talking to Simon from school about this and he asked the same question. The way I see it: no. It doesn’t make a noise because noise is only a construct of our mind. The tree makes the vibrations, but those vibrations aren’t really noise until we perceive them as such. Some may ask if it makes a noise if that recording is then played to someone who constructs the noise from the recording. But then it isn’t the tree making the noise and we aren’t building the construct from the tree’s vibrations but rather listening to an encoding, and experiencing the recording.

  3. Kent said,

    Is the tree there if you look at it? Does it disappear if you turn around?

  4. toto said,

    Are you implying my argument says that trees wouldn’t exist if we couldn’t sense the electromagnetic waves they reflect? So if we hadn’t developed sight the world wouldn’t exist? absurd.

    No, the tree is there whether we look at it or not. It reflects electromagnetic waves but that is not sight/vision, it is not sight unless it is seen. Sight is simply the way our mind perceives part of the spectrum.

    If the tree falls it will make vibrations whether we hear it or not. But unless we experience these vibrations they just remain vibrations… they don’t becomes sound because sound is something we perceive, it’s a construct of our mind.

  5. Kent said,

    No, I don’t see the difference. Sound is a synonym for ‘vibrations’; sight, a synonym for electromagnetic radiation in that particular part of the spectrum. Saying that the world is silent unless there are minds to make it full of noise is as absurd as saying the world is blank without eyes to make it full of spectacle.

    Can’t you see the parallel I’m drawing. You say sound is a construct of the mind; I’m saying vision is as well! Why are sound waves (and waves is what they are), any different to light?

    In any case, the tree-falling-in-forest riddle is a philosophical one in epistemology, about whether the world has reality – and what kind of reality – beyond perception, which remains unanswered by this thread (we’re both falling firmly on the side that it does).

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