What Wittgenstein is challenging is the dominant notion in contemporary philosophy that meaning can be reduced to propositions, that there is some underlying logic to our language which it is somehow the business of the philosopher to discover. To a large extent, this was Wittgenstein's position in his earlier work,...
What Wittgenstein is challenging is the dominant notion in contemporary philosophy that meaning can be reduced to propositions, that there is some underlying logic to our language which it is somehow the business of the philosopher to discover. To a large extent, this was Wittgenstein's position in his earlier work, most notably in the Tractatus. However, he subsequently abandoned that position to argue for meaning as being intimately bound up with how we use ordinary language in our daily lives.
Let us take a brief example from Wittgenstein to illustrate the point. Although we can define a tree, for instance, for the purposes of scientific classification or compiling a dictionary, that definition is itself dependent on how we have already been using the word "tree" in our everyday language. In other words, we do not know what a tree is only because we read about it in a science book or a dictionary, we know about it because we have direct experience of trees and have been able to share that experience with others by way of language.
According to Wittgenstein, this approach is the exact opposite of how many philosophers have traditionally looked at the matter. They seek to establish a logical definition of something, but the object in question is already being experienced, talked about, and understood. They have things the wrong way round, and the resulting confusion helps to explain why there are so many seemingly unsolvable problems in philosophy. Concepts do not need to be clearly defined in order to be meaningful.
The later Wittgenstein, then, sees most of the problems of philosophy as being related to a misunderstanding and misuse of language. Meaning is not something that can be crystallised into a neat propositional structure by speculative philosophers. Instead, we need to look at how language is used in the many different human discourses or language games, as Wittgenstein calls them.
Each language game has its own unwritten rules. However, these rules are themselves determined over time by custom and usage. They are not set down in advance. We learn the rules simply by playing the game and by participating in each specific discourse. There are many different language games, and each one has different rules. The language game of, say, theology, will be completely different from the language game of science; the language game of engineering will be different from the language game played by high school students and so on.
Although there is a bewildering array of different language games, they all have one thing in common: they are public. This is to say that their meaning is one that can be shared by others. Otherwise, it would not be possible for players in each language game to communicate with each other in any meaningful sense. In fact, language games would not even be possible in the first place.
That being the case, there can be no such thing as a private language. For language to have any kind of meaning, it needs to be communicated and shared. Even if my friend and I are the only two people in the world who understand each other, there still needs to be some way of communicating between ourselves. In other words, although our language game would only consist of two players, it would still need to be public, it would still need to be shared, and it would still be based on certain rules derived from usage over time.