The Problem of Common Knowledge

Communication is a form of social interaction; in particular, it is a type of overt interaction be­tween two (or more) agents, one meaning something by a certain action and the other(s) abduct­ing to its presumed meaning. Since each party knows that the first agent relies, on making her move, on the partner's ability to comprehend it and each also knows that both know that she does, communication is somehow a circular process. This circularity is generally captured as the idea that communication requires that some knowledge be shared among the participants, but there are crucial differences as to the details of this idea.

Let us reconsider the umbrella episode of "Mentalist Theories of Communication": Ann glances out of the window and says "I think it's about to rain"; Bob then decides to take an um­brella with him. According to Grice (1957), as we have seen, this is an instance of communica­tion if Ann, by her utterance: (1) intends to induce Bob to take an umbrella — or anyway to act so as to avoid getting drenched with rain; (2) intends Bob to recognize intention (1); (3) intends that recognition to be (part of) Bob's reasons for taking an umbrella; and if Bob recognizes Ann's intentions (1) - (3) in his turn.

Strawson (1964) remarks that a further condition is needed to rule out certain noncommu-nicative counterexamples, namely that Ann: (4) intends Bob to recognize intention (2).

Schiffer (1972) then shows that even this will not do, and that it is also necessary that Ann: (5) intends Bob to recognize intention (3); (6) intends Bob to recognize intention (4); (6) intends Bob to recognize intention (5); and so on ad infinitum so that true communication will only oc­cur when the first agent has, for each nth intention of this type, an additional (n + 1)th intention that n be recognized by the partner, and when the latter recognizes each of these (n + 1) inten­tions in his turn. The virtual endpointof this infinite succession of mental states is called mutual knowledge and is supposed to provide the firm ground that the interlocutors need to rely on if they are to communicate safely.

There are, however, serious problems with Schiffer's argument. First, even the simplest communicative act would require an infinite stream of intentions on the one side and a corre­spondingly infinite stream of acts of recognition on the other side. Obviously, neither feat could be accomplished by a real-world agent (Clark & Marshall 1981). Furthermore, each agent could safely rely on common knowledge only if the partner actually entertained all the relevant mental states, which would in turn require the existence of a suitable confirmation procedure plus in­finite time to implement it. Once again, neither condition could ever be satisfied in the real world (Sperber & Wilson 1986).

We are thus faced with a dilemma. On the one hand, any conception of common knowledge as the endpoint of an infinite conjunction of nested mental states of the Ann believes that Bob believes that Ann... kind is untenable. On the other hand, to limit the chain to an arbitrarily fi­nite length (as proposed by Grice himself, 1982) or to simply do away with common knowl­edge and let condition (1) be sufficient for the definition of communication (as proposed by Sperber & Wilson 1986) would not rule out Strawson's and Schiffer's counterexamples, so that the difference between what is communication and what is not would be missed.

 

Беседа «Как поступить?»

Беседа «Как поступить?» является адаптированным Г.А. Урунтаевой, Ю.А. Афонькиной вариантом и представляет собой комплекс вопросов:

- Нужно ли делиться игрушками с другими детьми? Почему?

- Нужно ли принимать в свою игру других детей, если они просят об этом? Почему?

- Можно ли драться, если другой ребенок отобрал у тебя игрушку? Почему?

- Можно ли без спроса брать чужие вещи? Почему?

- Можно ли шуметь, когда другие отдыхают? Почему?

- Можно ли вертеться на занятиях, мешать заниматься другим детям? Почему?

2. Опрос детей на тему «Права ребенка»

- Знаешь ли ты, что у каждого ребенка есть свои права?

- Как ты думаешь, что такое право?

- Как ты понимаешь слова «иметь право»?

- Какие права есть у тебя и других детей?

- Кто защищает права детей?

- Можешь ли ты сам защитить свои права и права других детей?

- Что такое обязанность? Какие обязанности есть у тебя?