I want now to return to the problem which I raised earlier (Section 6) of how far we can distinguish the logic of technical actions from the pseudo-logic of expressive actions.

In our own Western, literate, mechanically organised society, so much ‘true’ Aristotelian logic is built into the cultural system that we mostly take it for granted that logic of this kind is an essential component of common sense. Yet in practice we only exploit formal logical principles in the relatively rare instances in which we are seeking to convey exact information at a distance using a single channel of communication, as in writing a letter or a book or speaking to someone over the telephone. When two people are in face to face communication, so that they can use several channels of sensory information simultaneously – touch, sight, hearing and so on – the logical ordering of individual messages is much less obvious.

If you record unrehearsed conversation on tape you will find that on play-back very little of it is immediately comprehensible; yet, in context, all those present would have understood what was being said. This is because, in its original setting, the spoken utterance was only part of a larger whole. It had a metonymic (sign) relationship with everything else that was going on in the room at the same time, and this non-verbal ‘other’ was also conveying part of the message.

But the same argument applies the other way round. When an anthropologist tries to decode a set of non-verbal indices he needs to remember that he has only got part of the evidence.