Informationtheory provides a rigorous formalism to understand and quantify interaction via the concept ofpassing messages through a noisy channel.

This con-cept, communication of information, is rooted in information theory (Chapter 17).

Intentionality is a litmus test for HCI theories.

One type of determination is shared by all theories of interaction in HCI: teleological determina-tion.

For example, interaction-as-tool-usefocuses on this idea (Chapter 19). Tools change people and their activities; in turn, this changesthe tools.

In other words, they must be about mutual determinacy.

In HCI, propositions must generally link aspects of people with aspects of technology or design.

The theory starts with a high-level statement: The motorsystem is a limited-capacity channel. From there, it derives propositions about the relationshipbetween performance and interface design through the construct of a target.

Theories of interaction illuminate interactive phenomena beyond intuition and helpsolve design and engineering problems in HCI.

Such a view of how theory functions in an interpretive science suggests that the distinction, relative in any case, that appears in the experimental or observational sciences between "descrip­tion" and "explanation" appears here as one, even more relative, between "inscription" ("thick description") and "specification" ("diagnosis")-between setting down the meaning particular social actions have for the actors whose actions they are, and stating, as explicitly as we can manage, what the knowledge thus attained demonstrates about the society in which it is found, and beyond that, about social life as such. Our double task is to uncover the conceptual struc­tures that inform our subjects' acts, the "said" of social discourse, and to construct a system of analysis in whose terms what is generic to those structures, what belongs to them because they are what they are, will stand out against the other determinants of human behavior. In ethnog­raphy, the office of theory is to provide a vocabulary in which what symbolic action has to say about itself-that is, about the role of culture in human life-can be expressed.

conceptualization is directed toward the task of generating interpretations of matters already in hand, not toward projecting outcomes of experimental manipulations or deducing future states of a determined system. But that does not mean that theory has only to fit (or, more carefully, to generate cogent interpre­tations of) realities past; it has also to survive-intellectually survive-realities to come. Although we formulate our interpretation of an outburst of winking or an instance of sheep­raiding after its occurrence, sometimes long after, the theoretical framework in terms of which such an interpretation is made must be capable of continuing to yield defensible interpretations as new social phenomena swim into view

The first is the need for theory to stay rather closer to the ground than tends to be the case in sciences more able to give themselves over to imaginative abstraction. Only short flights of ratiocination tend to be effective in anthropology; longer ones tend to drift off into logical dreams, academic bemusements with formal symmetry. The whole point of a semiotic approach to culture is, as I have said, to aid us in gaining access to the conceptual world in which our subjects live so that we can, in some extended sense of the term, converse with them. The tension between the pull of this need to penetrate an unfamiliar universe of symbolic action and the requirements of technical advance in the theory of culture, between the need to grasp and the need to analyze, is, as a result, both necessarily great and essentially irremovable.