Wittgenstein’s Blue and Brown Books: What Can Be Said About Computational Thinking

“Perhaps one of the most outspoken of the pre-test critics was Turing’s close colleague and friend, Ludwig Wittgenstein.” (1, 433)

As some accounts suggest, “fundamentally, he really disliked the idea that people were machines.” (1, 434)

Empirical Thinking vs Philosophical Critique

The central question here is whether it is possible to say that humans compute while experiencing mental processes. Is a computational theory of thinking even meaningful? Most researchers agree that Turing and Wittgenstein had different perspectives on this point — but in what exact sense?

As Margaret Boden notes, “the whole tenor of Wittgenstein’s mature philosophy suggests that he wouldn’t have welcomed computational work on language.” (3, 676)
Let’s take a closer look at why that might be.

We remember from our last discussion of Turing that he provided empirical criteria for thinking. That is, if a machine satisfies complex behavioral criteria, then it qualifies as “thinking.” Any other approach, he believed, is absurd — since all we can rely on is observable empirical data.

For Wittgenstein, by contrast, the idea that machines can think seems nonsensical — like suggesting that numbers can have colors (2). He also rejected attempts to define complex entities such as consciousness or mind in a systematic way. In this respect, his stance may appear behaviorist. However, he also firmly opposed the notion that words carry fixed, machine-readable definitions. Quite the opposite.

The core argument throughout The Blue and Brown Books (and later, Philosophical Investigations) is that symbols have no stable, predetermined meaning. Wittgenstein devoted his mature work to exploring how meaning is created within natural language.

Consider the contrast with machines: they receive tables of words and explicit instructions for how to use them. But is this how humans use words? Do such rules really exist? One of the first computer programs was designed for translation. Yet a truly capable translation machine — especially one that avoids word-for-word substitutions or statistical shortcuts — would require a universal grammar or an artificial interlingua to mediate between languages. It would also need detailed, formalized grammars for the natural languages involved (3, 678).

Wittgenstein points to a different view. We often make the mistake of seeking the meaning of a word as though it were an object located beside the word itself. This confusion, he says, stems partly from our habit of expecting every noun to refer to a “thing.” But in reality, a sentence gets its meaning from the language system it belongs to. To understand a sentence is not to decode isolated signs — it is to participate in a broader language practice (2).

What Is Meaning?

In the Blue Book, Wittgenstein emphasizes that in ordinary practice, we do not use language by following strict formal rules — nor were we taught language in this way. Nevertheless, when we reflect philosophically, we tend to imagine language as a formal calculus, bound by rigid definitions and clear-cut procedures. He critiques this as a misleading and one-sided view. In most cases, we cannot even articulate the rules we are supposedly following — because, quite often, no such fixed rules exist (2).

We tend to imagine language as if it were something precise and mathematical — something that operates like logic or code. This image works well in scientific or technical contexts. But Wittgenstein invites us to look more carefully: how does language actually function in our lives?

Take, for example, Wittgenstein’s now-famous reference to the question “What is time?” Philosophers such as St. Augustine have struggled with it for centuries. At first glance, it appears to demand a definition. But what would such a definition really give us? Often, it leads only to more abstract or vague terms. Why are we troubled by our inability to define “time,” yet not by our inability to precisely define something like a “chair”? Why does one confuse us, while the other does not?

Language Games

Wittgenstein’s insight is that meaning isn’t fixed or mechanical. It does not emerge from flawless definitions or abstract systems. Instead, meaning arises from how we use words in concrete, everyday settings — from the messy, flexible, and social nature of human language. Words make sense because of the roles they play in our shared forms of life, not because they exist within an idealized semantic system waiting to be decoded.

This confusion, he suggests, often begins when we assume that mental processes — like believing, hoping, or thinking — must exist independently from how we express them. But Wittgenstein proposes a shift in perspective: rather than searching for the mental event inside the mind, we should observe how a thought is expressed in language.

He offers a useful rule of thumb: if you’re confused about what a belief or thought is, try replacing it with its expression — that is, what someone actually says or does. This subtle shift can fundamentally change our understanding of what thinking even is.

Language works in the same way. Words do not carry fixed meanings; rather, they derive meaning from use. And this use depends on the kind of “language game” being played — whether someone is asking a question, telling a joke, giving an order, or offering an explanation. There is no universal grammar of all language. Instead, there exists a rich variety of overlapping and evolving practices.

The Blue and Brown Books were originally a series of lectures, transcribed by Wittgenstein’s students. There is no clear evidence that he ever intended to publish the Brown Book. As Ray Monk notes:

“Perhaps he was then planning to leave philosophy altogether to take up manual work in Russia. It represents an attempt to present the result of his seven years’ work in philosophy in a way that would enable someone else (perhaps Waismann) to make use of them.” (4, 348)

Bibliography

1. Pertti Saariluoma & Matthias Rauterberg (2015). In ICAI 15: 17th International Conference on Artificial Intelligence, pp. 433–437.
2. Ludwig Wittgenstein. The Blue and Brown Books. Oxford, 1958.
3. Margaret Boden. Mind As Machine: A History of Cognitive Science, Oxford University Press, 2006.
4. Ray Monk. Ludwig Wittgenstein: The Duty of Genius. Routledge, 2012.
5. Robert M. French (2012). “Moving Beyond the Turing Test.” Communications of the ACM, Vol. 55, No. 12, pp. 74–77.
6. Diane Proudfoot (2024). “Wittgenstein and Turing on AI: Myth versus Reality,” in Wittgenstein and Artificial Intelligence, Volume 1: Mind and Language.

Image: Ludwig Wittgenstein and Francis Skinner in Cambridge
Date: Before 1941
Author: Anonymous (likely a student photographer)
Source: Wikimedia Commons (public domain)