The Blue and Brown Books are two sets of notes taken during lectures conducted by Ludwig Wittgenstein from 1933 to 1935. They were mimeographed as two separated books, and a few copies were circulated in a restricted circle during Wittgenstein's lifetime. The lecture notes from 1933–1934 were bound in blue cloth, and the notes dictated in 1934–1935 were bound in brown. Rush Rhees published these together for the first time in 1958 as Preliminary Studies for the "Philosophical Investigations". Inchoate versions of many of the ideas that would later be more fully explored in the Philosophical Investigations are found there, so these offer textual evidence for the genesis of what became known as Wittgenstein's later philosophy.
''The Blue Book''
The Blue Book was dictated from 1933 to 1934, and contains certain themes unaddressed in Wittgenstein's later works, including deliberations on thinking as operating with signs. An early conception of what would later become known as language-games is present in the text, which represents the first period of Wittgenstein's thought after 1932, a method of linguistic analysis which would later become ordinary language philosophy. While Wittgenstein in The Blue Book is not dogmatic nor systematic, he does provide arguments that point toward a more self-critical view of language. For example, he does not think that "understanding" and "explaining" are necessarily related. He suggests that when humans are learning a language-game they are actually being trained to understand it. He writes: "If we are taught the meaning of the word 'yellow' by being given some sort of ostensive definition this teaching can be looked at in two different ways: The teaching is a drill. This drill causes us to associate a yellow image, yellow things, with the word 'yellow.' Thus when I gave the order 'Choose a yellow ball from this bag' the word 'yellow' might have brought up a yellow image, or a feeling of recognition when the person's eye fell on the yellow ball. The drill of teaching could in this case be said to have built up a psychical mechanism. This, however, would only be a hypothesis or else a metaphor. We could compare teaching with installing an electric connection between a switch and a bulb. The parallel to the connection going wrong or breaking down would then be what we call forgetting the explanation, or the meaning, of the word...t is the hypothesis that the process of teaching should be needed in order to bring about these effects. It is conceivable, in this sense, that all the processes of understanding, obeying, etc., should have happened without the person ever having been taught the language; The teaching may have supplied us with a rule which is itself involved in the processes of understanding, obeying, etc.: 'involved,' however, meaning that the expression of this rule forms part of these processes..." As the citation suggests, Wittgenstein views understanding a language-game as being mostly concerned with training. Having said that, Wittgenstein is not one to believe that even understanding a language-game can be reduced to one process; like the plethora of language-games available to human beings, there are also plethora of "understandings." For example, the "understanding" of a language may come about by the "drilling" of the association between the word "yellow" and a yellow-patch; or it may involve learning rules, like rules used in the game of chess. Moreover, Wittgenstein doesn't think that humans use language mechanically, as if following a calculus. He writes in The Blue Book, "n general we don't use language according to strict rules--it hasn't been taught us by means of strict rules, either." Wittgenstein clarifies the problem of communicating using a human language when he discusses learning a language by "ostensive defining." For example, if one wanted to teach someone that a pencil was called a "pencil" and pointed to a pencil and said, "pencil," how does the listener know that what one is trying to convey is that the thing in front of me is called a "pencil"? Isn't it possible that the listener would associate "pencil" with "wood"? Maybe the listener would associate the word "pencil" with "round" instead. Wittgenstein writes regarding several possible "interpretations" which may arise after such a lesson. The student may interpret your pointing at a pencil and saying "pencil" to mean the following: This is a pencil; This is round; This is wood; This is one; This is hard, etc., etc.
''The Brown Book''
During the academic year 1934–1935, Wittgenstein dictated to Francis Skinner and Alice Ambrose a text of which three copies were typed and bound. Later it became known as The Brown Book. Wittgenstein contemplated publishing and attempted a German revision, but ultimately abandoned the project as worthless.
Possible further book
A further item called The Pink Book or The Yellow Book has been speculated to exist, and may be contained in an archive of papers that Wittgenstein posted to a friend of Skinner days after his death.
In the film Ex Machina, the name of the company designing the artificial intelligence is named 'Blue Book' after Wittgenstein's set of notes, and it is loosely modeled on Google.
