After the publication of the Tractatus, Wittgenstein felt he had nothing more to contribute to philosophy. He spent the 1920s in a variety of jobs. He was a schoolteacher in a small Austrian village, a gardener, and an amateur architect. During this time, he still had some connection with the philosophical world, notably in his conversations with Frank Ramsey on the Tractatus that gradually led him to recognize that this work was flawed in a number of respects. In the late twenties, he also came into contact with the Vienna Circle of logical positivists who were greatly inspired by his work on the Tractatus.
Somewhat reluctantly, Wittgenstein accepted a teaching position at Cambridge in 1929 (the Tractatus was submitted as his doctoral dissertation), and spent most of the rest of his life there. He remained skeptical about philosophy, and persuaded many of his students to pursue more practical careers in medicine or elsewhere. Throughout the thirties and early forties, he worked out his more mature philosophy, but did not publish.
Wittgenstein wrote in a series of painstakingly edited notebooks. He would constantly revise, cut, and edit, going through more than a dozen drafts before he arrived in 1945 at what is now published as the first part of the Philosophical Investigations. The same process went into the formation of Part II of the work, though it never reached a state that Wittgenstein felt was ready for publication. Wittgenstein insisted that his work not be published until after his death; he succumbed to cancer in 1951, and the Investigations were published in 1953. Following their publication, a number of writings culled from Wittgenstein's notebooks or from lecture notes taken by his students at Cambridge were also made public. These include the Remarks on the Foundations of Mathematics, On Certainty ,three volumes on the philosophy of psychology, and The Blue and Brown Books, which collect a series of lectures he dictated in the early 1930's.
The Philosophical Investigations were completed and then published in a Europe that was just emerging from the shadow of the Second World War. A general sense of malaise pervaded Western Europe as it slowly set about rebuilding and coming to terms with the scale of destruction that had been wreaked. At the same time, the Soviet Union had cemented its hold on Eastern Europe, had developed the nuclear bomb, and was rapidly working toward launching rockets into space. People feared that Europe would be dominated by communism.
This malaise and reconstruction was reflected not only in politics, but also in the arts and letters. The holocaust and the devastation of the war had soundly demolished the 19th century myth of evolution and progress. In a world that made increasingly little sense to the people in it, narratives meant to explain and justify the course of history or the arts on a grand scale no longer seemed plausible.
There is no straightforward definition of postmodernism, but Wittgenstein's piecemeal approach of language-games, his critique of the notion of ultimate grounds of justification, and his mistrust of general statements about the world or the meanings of words may be seen as characteristic of postmodern thought.
In abandoning logic, Wittgenstein abandons one of the primary tools of analytic philosophy, thus breaking with the tradition established by Frege and Russell. Nonetheless, Wittgenstein's emphasis on the significance of language is inherited from these predecessors.
Wittgenstein is also deeply concerned with the growing field of psychology. William James, one of the pioneers of modern psychology, receives as much mention by name as any other thinker in the Investigations. Psychology was being established as a scientific field with its own experimental method, and any failures of psychological methodology were passed off as the growing pains of a science in its infancy. The Investigations deal at length with the fear that psychology is on the wrong track altogether because its fundamental ideas contain deep philosophical confusion.
Another strain we can detect in the Investigations is an interest in the ultimate grounds of justification. If one proposition can only be justified by a second, more certain proposition, how can we find propositions that are themselves absolutely certain and thus not needing justification? Logical positivism in particular sought to distinguish sharply between synthetic and analytic propositions, the former stating facts and the latter outlining the rules or linguistic framework in which synthetic propositions could be justified. Wittgenstein addresses logical positivism as much as anything else when he criticizes the idea that there must be an ultimate ground of justification.
The Investigations open with a quote from St. Augustine's Confessions, which describes the process of learning language in terms of learning the names of objects. It appears that there is nothing wrong with saying that words name things and that we teach people the meanings of words by pointing to the objects that they name. The trouble arises when we take this connection between word and thing as the fundamental relationship that fixes language to the world. This relationship can only be seen to exist once a great deal of the machinery of language, context, and usage are already in place. We would not say the words in a four-word language between builders, consisting of "block!" "pillar!" "slab!" and "beam!" are names of objects, because they can only be understood as such in contrast to names of colors, prepositions, adjectives, and the like. Meaning is not fixed by the relationship between words and things, but by how words are used.
The Investigations have a peculiar literary style that is difficult to characterize. Very little of Wittgenstein's writing even resembles standard philosophical argument. Instead, we get questions, hesitant hypotheses, doubts, temptations, and the like. Instead of giving us a monologue in which he lays out his position, Wittgenstein engages us in a dialogue with an interlocutor. The interlocutory voice, usually (but not always) found in quotation marks, is the driving force that propels the Investigations forward. The interlocutor voices the temptations that are liable to lead us into philosophical theorizing. In any given section of the text, the interlocutory voice raises objections to Wittgenstein's anti-metaphysical outlook, and Wittgenstein responds to these objections. By means of this dialogue, Wittgenstein does not bring us to any definite answers, but to an end to questioning.
One of the major themes in the early sections of the text (particularly sections 65–91) is that the meanings of words are not rigidly defined. Wittgenstein uses the example of "game," showing us that there is no catch-all definition that will include everything we call a game and exclude everything that we do not call a game. This conclusion can be, and is, extended to a wide range of terms that philosophers often try to include within a single definition: "language," "understanding," "meaning," "reading," "seeing," and so on. This position reflects Wittgenstein's remark at section 43 that the meaning of a word is determined by its use. Definition is not something prior to the use of a word that fixes its meaning and determines how it will be used. Rather, definition is a descriptive tool that reflects the various ways a word is used.
This criticism of the notion of fixity of meaning sets the stage for Wittgenstein's work in the later sections of the book to show that there is no mental state or process that corresponds to such concepts as "meaning," "understanding," "believing," and so on. If there is not one fixed meaning or use for these words, then they cannot possibly refer to a single, fixed concept.
The Investigations are difficult to understand not only because they introduce a number of unfamiliar themes and methods, but also because these themes and methods are introduced in the service of a new conception of what philosophy ought to do. The Investigations consist to a large extent of an extended criticism of old ways of philosophical thinking. Philosophy has generally concerned itself with metaphysical theories and deep explanations that cut to the core of the concepts that govern human life and reality. Wittgenstein suggests that this kind of theorizing can only lead us astray: there are no concepts or explanations hiding beneath the surface of everyday phenomena. These metaphysical theories are built upon unwarranted assumptions or generalizations, often born out of the structure of our grammar. The purpose of Wittgensteinian philosophy is to lead us to recognize these temptations toward metaphysical thinking, and to learn to subdue them.
This is not to say that we are better off not doing philosophy at all, or that Wittgenstein represents an end to philosophy. Wittgenstein's "therapeutic" method of identifying temptations and then showing them to be mistaken does not simply bring us back to where we were before we started thinking philosophically. Some philosophers have identified Wittgenstein's method as a method of self-knowledge. It brings us to a deeper understanding of ourselves, our thoughts, and our temptations. The kinds of temptations Wittgenstein identifies do not only crop up when we sit down to study philosophy; they are a general characteristic of abstract thinking. As long as we wish to think abstractly, we are liable to commit the sorts of errors Wittgenstein identifies. His concept of philosophy is a honed method by which we can avoid this sort of error.
We commonly think of the role of justification as providing a definite ground for holding the beliefs, claims, etc., which we are justifying. Wittgenstein's discussion of rule following in sections 185–242 is the foremost among a number of discussions that show us that justification plays no such role. If we accept that every rule is open to various possible interpretations (for instance, "—>" could mean "go left" or "go right"), then every rule will require a deeper level of justification— another rule—to fix which is the correct interpretation. But then, that further rule is also open to various interpretations. If any given rule is open to various possible interpretations, there is no ultimate ground of justification upon which the correct interpretation can be fixed.
Wittgenstein does not conclude that there is no ultimate justification or correct interpretation. Rather, he suggests that we are looking for the wrong thing when we look for ultimate grounds of correctness. The mistake we make is in accepting that every rule is open to various possible interpretations. The sign, "—>" is not open to various interpretations: we never stop to wonder if it means "go left" or "go right." Interpretation and justification are not applicable to everything, nor do they serve to determine correctness. They are only called upon in genuine cases of ambiguity where we do not know how to go on without a justified interpretation.
The theme of privacy is most explicitly discussed in sections 250–300, but it runs throughout the rest of the Investigations. It is difficult to articulate clearly what Wittgenstein is doing here, largely because he is dealing with ideas that he shows are largely inarticulate. Roughly speaking, he sets about deconstructing the mystification we feel when faced with peculiarities of the inner life.
Wittgenstein devotes a great deal of the Investigations to the peculiarities of talking about our inner sensations. On one hand, it seems an obvious truism that I have a kind of access to my own sensations that other people do not. On the other hand, Wittgenstein shows us that any attempt to formulate this truism as a substantial metaphysical fact is doomed. Though I uncontrovertibly experience my pains in a way that no one else does, I cannot talk about them in terms of "knowledge," because claims about knowledge presuppose that there is something to be known, and hence something that might not be known. My relationship to my inner sensations is not one of knowing, because I could not but experience them. We misunderstand this fact when we claim that other people have limited or only "indirect" knowledge of my inner sensations. Other people's knowledge seems limited in comparison to my own knowledge, but if we accept that what I have is not knowledge, then these limits disappear.