Wittgenstein's philosophy is a fusion of two very different traditions. On the one hand, Anglo-Saxon analytical philosophy, with its emphasis on logic, empiricism, and scientific faith. On the other hand, the culture of Vienna, both the proud artistic tradition of the 19th century and the bold innovations of the early 20th century. In addition, he was influenced by Schopenhauer, Kierkegaard, and Tolstoy.

Throughout his career, the relationship between language and reality is central to Wittgenstein. What is it to say something, and where are the boundaries between the meaningful and the meaningless?

His first major work, Tractatus logico-philosophicus , was first published in 1921. It has a distinctive style: 70 pages of numbered propositions, no explanations or examples. The work is systematic and aphoristic at the same time.

The Tractatus has two parts: what is written there, and what is not written there. According to Wittgenstein himself, the second was the most important. On the surface it is mostly a work of logic. Central is the image theory. Sentences depict cases in the world. This factual language, which is used in science, defines the limits of what can be meaningfully said.

But this is not all. The most important thing is what cannot be said, at least not with such descriptive sentences, precisely because it is not about facts in the world. These are questions of ethics and the meaning of life. These things cannot be said, only shown, for example in poetry or music.

The Tractatus had a great influence, especially on what is called the Vienna Circle and their logical empiricism. But Wittgenstein thought they had misunderstood his work. In any case, he himself came to the conclusion that the Tractatus had shortcomings. However, it had not solved all philosophical problems, as he first thought. Now his thinking went in a different direction.

The best-known work of his late philosophy is Philosophical Investigations , first published after his death. This book is different from the Tractatus in form, but equally original, and equally far from the usual philosophical style. Like many of his later writings, this book consists of a series of notes, with questions, dialogues, similes, examples, and metaphors.

While the young Wittgenstein investigated the relationship between language and the world through logic, Wittgenstein now sees language as part of the life of action. Words and expressions have their meaning through the social contexts in which they are part, what he also calls language games. And ultimately, it is the human way of life that constitutes the limits of linguistic meaning.

Although there are differences, there are also similarities between the young and the late Wittgenstein. Throughout his life, Wittgenstein thought of philosophy as an activity, not as a theory or system. In his late philosophy, he even compares philosophy to therapy. Philosophical problems arise because we get confused and lost in language. His task is to show the fly out of the fly's glass, he says.

Tractatus and Philosophical Investigations are his two best-known works. But he wrote more, much more, thousands of pages of philosophical notes. Some of these have been collected and published as books. The scholarly edition of his entire "Nachlass" is being published in digital form by the University of Bergen in collaboration with Oxford University Press.