trained to be a school teacher and taught primary school for a number of years in the mountains of lower Austria. In the mid-1920s he also built a house for his sister; this can be seen as an attempt to give visual expression to the logical, aesthetic, and ethical ideas of the Tractatus. In those years he developed a number of interests seminal for his later development. His school experience drew his attention to the way in which children learn language and to the whole process of enculturation. He also developed an interest in psychology and read Freud and others. Though he remained hostile to Freud’s theoretical explanations of his psychoanalytic work, he was fascinated with the analytic practice itself and later came to speak of his own work as therapeutic in character. In this period of dormancy Wittgenstein also became acquainted with the members of the Vienna Circle, who had adopted his Tractatus as one of their key texts. For a while he even accepted the positivist principle of meaning advocated by the members of that Circle, according to which the meaning of a sentence is the method of its verification. This he would later modify into the more generous claim that the meaning of a sentence is its use.
Wittgenstein’s most decisive step in his middle period was to abandon the belief of the Tractatus that meaningful sentences must have a precise (hidden) logical structure and the accompanying belief that this structure corresponds to the logical structure of the facts depicted by those sentences. The Tractatus had, indeed, proceeded on the assumption that all the different symbolic devices that can describe the world must be constructed according to the same underlying logic. In a sense, there was then only one meaningful language in the Tractatus, and from it one was supposed to be able to read off the logical structure of the world. In the middle period Wittgenstein concluded that this doctrine constituted a piece of unwarranted metaphysics and that the Tractatus was itself flawed by what it had tried to combat, i.e., the misunderstanding of the logic of language. Where he had previously held it possible to ground metaphysics on logic, he now argued that metaphysics leads the philosopher into complete darkness. Turning his attention back to language he concluded that almost everything he had said about it in the Tractatus had been in error. There were, in fact, many different languages with many different structures that could meet quite different specific needs. Language was not strictly held together by logical structure, but consisted, in fact, of a multiplicity of simpler substructures or language games. Sentences could not be taken to be logical pictures of facts and the simple components of sentences did not all function as names of simple objects. These new reflections on language served Wittgenstein, in the first place, as an aid to thinking about the nature of the human mind, and specifically about the relation between private experience and the physical world. Against the existence of a Cartesian mental substance, he argued that the word ‘I’ did not serve as a name of anything, but occurred in expressions meant to draw attention to a particular body. For a while, at least, he also thought he could explain the difference between private experience and the physical world in terms of the existence of two languages, a primary language of experience and a secondary language of physics. This duallanguage view, which is evident in both the Philosophical Remarks and The Blue Book, Wittgenstein was to give up later in favor of the assumption that our grasp of inner phenomena is dependent on the existence of outer criteria. From the mid-1930s onward he also renewed his interest in the philosophy of mathematics. In contrast to Frege and Russell, he argued strenuously that no part of mathematics is reducible purely to logic. Instead he set out to describe mathematics as part of our natural history and as consisting of a number of diverse language games. He also insisted that the meaning of those games depended on the uses to which the mathematical formulas were put. Applying the principle of verification to mathematics, he held that the meaning of a mathematical formula lies in its proof. These remarks on the philosophy of mathematics have remained among Wittgenstein’s most controversial and least explored writings.
Later period. Wittgenstein’s middle period was characterized by intensive philosophical work on a broad but quickly changing front. By 1936, however, his thinking was finally ready to settle down once again into a steadier pattern, and he now began to elaborate the views for which he became most famous. Where he had constructed his earlier work around the logic devised by Frege and Russell, he now concerned himself mainly with the actual working of ordinary language. This brought him close to the tradition of British common sense philosophy that Moore had revived and made him one of the godfathers of the ordinary language philosophy that was to flourish in Oxford in the 1950s. In the Philosophical Investigations Wittgenstein emphasized that there are countless different uses of what we call ‘symbols,’ ‘words,’ and ‘sentences.’ The task of philosophy is to gain a perspicuous view of those multiple uses and thereby to dissolve philosophical and metaphysical puzzles. These puzzles were the result of insufficient attention to the working of language and could be resolved only by carefully retracing the linguistic steps by which they had been reached.
Wittgenstein thus came to think of philosophy as a descriptive, analytic, and ultimately therapeutic practice. In the Investigations he set out to show how common philosophical views about meaning (including the logical atomism of the Tractatus), about the nature of concepts, about logical necessity, about rule-following, and about the mind–body problem were all the product of an insufficient grasp of how language works. In one of the most influential passages of the book he argued that concept words do not denote sharply circumscribed concepts, but are meant to mark family resemblances between the things labeled with the concept. He also held that logical necessity results from linguistic convention and that rules cannot determine their own applications, that rule-following presupposes the existence of regular practices. Furthermore, the words of our language have meaning only insofar as there exist public criteria for their correct application. As a consequence, he argued, there cannot be a completely private language, i.e., a language that in principle can be used only to speak about one’s own inner experience. This private language argument has caused much discussion. Interpreters have disagreed not only over the structure of the argument and where it occurs in Wittgenstein’s text, but also over the question whether he meant to say that language is necessarily social. Because he said that to speak of inner experiences there must be external and publicly available criteria, he has often been taken to be advocating a logical behaviorism, but nowhere does he, in fact, deny the existence of inner states. What he says is merely that our understanding of someone’s pain is connected to the existence of natural and linguistic expressions of pain. In the Philosophical Investigations Wittgenstein repeatedly draws attention to the fact that language must be learned. This learning, he says, is fundamentally a process of inculcation and drill. In learning a language the child is initiated in a form of life. In Wittgenstein’s later work the notion of form of life serves to identify the whole complex of natural and cultural circumstances presupposed by our language and by a particular understanding of the world. He elaborated those ideas in notes on which he worked between 1948 and his death in 1951 and which are now published under the title On Certainty. He insisted in them that every belief is always part of a system of beliefs that together constitute a worldview. All confirmation and disconfirmation of a belief presuppose such a system and are internal to the system. For all this he was not advocating a relativism, but a naturalism that assumes that the world ultimately determines which language games can be played. Wittgenstein’s final notes vividly illustrate the continuity of his basic concerns throughout all the changes his thinking went through. For they reveal once more how he remained skeptical about all philosophical theories and how he understood his own undertaking as the attempt to undermine the need for any such theorizing. The considerations of On Certainty are evidently directed against both philosophical skeptics and those philosophers who want to refute skepticism. Against the philosophical skeptics Wittgenstein insisted that there is real knowledge, but this knowledge is always dispersed and not necessarily reliable; it consists of things we have heard and read, of what has been drilled into us, and of our modifications of this inheritance. We have no general reason to doubt this inherited body of knowledge, we do not generally doubt it, and we are, in fact, not in a position to do so. But On Certainty also argues that it is impossible to refute skepticism by pointing to propositions that are absolutely certain, as Descartes did when he declared ‘I think, therefore I am’ indubitable, or as Moore did when he said, ‘I know for certain that this is a hand here.’ The fact that such propositions are considered certain, Wittgenstein argued, indicates only that they play an indispensable, normative role in our language game; they are the riverbed through which the thought of our language game flows. Such propositions cannot be taken to express metaphysical truths. Here, too, the conclusion is that all philosophical argumentation must come to an