> Of course, the reason Wittgenstein ultimately rejected this picture, as in rejected describing the meaning of words by formal definition, is that it doesn't accurately describe the way language is used in practice, and leads us to misunderstand situations.

I don't think the author is really trying to give a "formal definition" of the meaning of words. The point he is trying to make is that while people may claim to disagree about a high level sentence like "when a tree falls and nobody is around to hear it, does it still makes a sound?", they actually don't expect there to be any real difference in the physical state of the world after the tree falls.

If you taboo the word "sound", then the question becomes either "when a tree falls and nobody is around to hear it, are there still vibrations in the air?" or "when a tree falls and nobody is around to hear it, is there still an auditory experience for anyone?" If two people were to disagree on either of THESE statements, then they actually have an important difference in their models of the world.

The idea is that words are just convenient ways of referring to a collection of objects that are similar in some ways. Words used in everyday conversation generally do not have strict definitions. They just refer to a cluster of things. This post helps explain that idea:

http://lesswrong.com/lw/nl/the_cluster_structure_of_thingspa...