Ludwig Wittgenstein’s Philosophical Investigations (1953) is an inquiry into the relation between meaning and the practical uses of language, and is also an examination of the relation between meaning and the rules of language. Wittgenstein explains how vague or unclear uses of language may be the source of philosophical problems, and describes how philosophy may resolve these problems by providing a clear view of the uses of language.

According to Wittgenstein, words are like tools in a tool-box. Words are instruments of language which may have varying uses, according to the purposes for which language may be used. The varying ways in which words may be used help to structure our concepts of reality.

Language is, in part, an activity of giving names to objects, or of attaching labels to things. For example, a builder may instruct an assistant as to what type of stone is needed for the construction of a building, by saying "slab" or "block" or "pillar" or "beam," according to the order in which the building-stones are needed, so that the assistant can bring the correct type of stone for the construction of the building. However, the naming of an object is only a preparation for an anticipated move in the language-game. Linguistic movement occurs when a sentence is constructed, such as, "Bring me a slab," or "Bring me a beam."

Wittgenstein describes language as a game in which words may be used in a multiplicity of ways: for example, to describe things, to ask questions, to report events, to speculate about events, to make requests, to give commands, to form hypotheses, to solve problems, and to perform other acts of communication.

The meaning of a word may be defined by how the word can be used as an element of language. A word may be given different meanings, according to how it is used in a language-game. However, the rules of a language-game may change, and different rules may be applied to different games. According to Wittgenstein, there is no single rule which is common to all games.

The rules of a game may (or may not) leave doubt about how the game should be played. The rules of a game may be definite or indefinite, clear or unclear. If the rules are unclear, then they may still be understandable enough to be used for playing a game.

Wittgenstein explains that the meaning of a word may not depend upon whether the word refers to something that actually exists. For example, if something ceases to exist, the word or name for that thing may still have meaning. If we say that the name for something exists, we may affirm that the name has meaning, even though the name may refer to something which no longer exists.

Thus, the word "pain" may have meaning, even if it refers to something which no longer exists. A person may understand what it means to have pain, even if he or she is not actually having pain.

Each word or name may be used in more than one language-game, and thus each word or name may have a family of meanings. A word or name may be useful without having a fixed meaning. The meaning of a word may be fixed or variable, definite or indefinite. A word or name for something may have multiple uses to express or designate that thing.

Words may be empty of meaning, or may have some meaning, or may be full of meaning. Words may be given meaning by the way in which they express thoughts and feelings. However, words may have different meanings when they are used differently to describe thoughts and feelings. Words may have either an essential or unessential (accidental) meaning, according to how they are used in a language-game.

Words may have a simple meaning, or may have a composite meaning. Simple aspects of meaning may be combined to produce composite aspects of meaning. Composite aspects of meaning may be combined to produce more complex aspects of meaning.

According to Wittgenstein, the meaning of a word is not what is referred to, or designated by, by that word, but is the use which the word has as an element of language. If we want to define the meaning of a word, we must define how the word is used an an instrument of language.

Some language-games may have definite rules, while others may not have definite rules.To the extent that language-games have similar rules, they may have `family resemblances.' To the extent that language-games do not have similar rules, words which are used in one game may not have the same meaning when they are used in another game.

Wittgenstein describes the activity of using language as similar to playing a game of chess. Words are like the pieces on a chessboard. Each word has a different use or function in the language-game.

Wittgenstein does not define what a `game' is, but gives examples of various games, such as chess, tennis, cricket, etc. Each game has its own set of rules, and each is played differently.

People who are playing a language-game, and who are playing by different rules, may have difficulty in understanding each other. People may have different interpretations of the rules, or may apply rules differently. People may, in some cases, decide the rules of a game while they are playing the game.

Wittgenstein says that the failure to understand words, or the failure to use words clearly, may often be caused by misunderstanding of how words are used in a language-game. Failure to communicate clearly may be caused by the use of words which have an unclear or indefinite meaning, or by lack of understanding of the relation between the meaning of words and the way in which they are used. The task of philosophy may be to clarify the uses of language, and to assemble `reminders of usage' concerning how rules are applied to language.

Wittgenstein also argues that the uses or meaning of words may change, according to changes in the circumstances and scene of a language-game. To use words meaningfully, people must decide which language-game they want to play, and how they want to play it.

Wittgenstein explains that when people communicate with each other, they may have to choose between a private language and a common language. The rules of a private language may not be the same as the rules of a common language. The meaning of words in a private language may not be the same as the meaning of words in a common language. People may need a common language in order to share an understanding of the meaning of words.

The connection between a word and its meaning may be arbitrary. For example, a person may arbitrarily choose to use the word "cold" to describe something which is warm, or to use the word "warm" to describe something which is cold. The use of the word "cold" to describe something which is warm, or the use of the word "warm" to describe something which is cold, may be meaningful if it is consistent with the rules of a language-game.

However, in some cases, the use of words may not be governed by any rules, or may occur beyond the limits of a language-game. In such cases, aimless or meaningless combinations of words may not be governed by the rules of any language-game.

Wittgenstein asserts that understanding of what is designated by a particular word may sometimes depend upon a previous experience of whatever is designated by that word. For example, to understand the meaning of the word "pain," it may be necessary to have experienced pain. In order to imagine another person’s pain, it may be necessary to recall one’s own previous experience of pain.

Understanding of the meaning of words may also depend on what is meant by the term "understanding." Meaning may be understood, but understanding (as an act of knowledge) may itself have meaning.

Wittgenstein, Ludwig. Philosophical Investigations. Translated by G.E.M. Anscombe. New York: The MacMillan Company, 1953.