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Three Propositions on Informational Cultures 23constituted by the husband, the wife, the prison, the prison guards,the cup of tea, the confederate, and the police gives rise to a closedset of messages. The confederate might have got away with it ormight have been caught; hence the uncertainty of the situation canbe expressed through a simple binary code (yes or no), that is one bit(or binary digit). However, the information source or sender (the wife)is limited in the information that she can send by the channel (thereis not much information that you can communicate through a cupof tea). Because the only transaction that is allowed between herselfand her husband is a cup of tea, then the latter is the channel andthe capacity of such a channel will put constraints on the coding ofthe uncertainty of the situation. For example, they might agree thatsweetened tea would be a yes and unsweetened would be a no.Of course, communication also includes the possibility of acorruption of the message in transit by noise. The jailer might havefigured out that the tea can be used as a means of communication andhe might interfere by telling the prisoner that he had sweetened ithimself. If the wife wanted to make sure that the message got through,she would thus need some way of inserting some redundancy intothe code, thus doubling the probability of the information survivingthe noise (she might have agreed also to add or not to add milk,for example). Although the code might be different, both casesare equally likely, so the amount of information that needs to betransmitted is ultimately low (a choice between two possibilitiesexpressible by way of a single bit). What the example illustrates isthe principle that, as Warren Weaver put it, ‘the unit informationindicates that in this situation one has an amount of freedom ofchoice, in selecting a message, which is convenient to regard as astandard unit amount.’ 25 The measure of the information that isproduced when the message is chosen from the set is the amount thatthe woman can communicate to her jailed husband. This amountof information can be reduced to the logarithm of the probabilitiesof the situation and thus be prepared for communication througha suitable channel. The value of information theory for cybernetics,according to Ross Ashby, lies exactly in its representing a givensituation as a set of mutually excluding alternatives. It does not askwhat individual answer it can produce, but ‘what are all the possiblebehaviours that it can produce’ and how likely one behaviour is whencompared to another. The value of information theory is that it dealswith such sets of probabilities.