To understand the account presented here, it is useful to distinguish two questions about information flow in a given system. What information flows through the system? Why does it flow? This book characterizes the first question in terms of a “local logic” and answers the second with the related notion of an “information channel.” Within the resulting framework one can understand the basic structure of information flow. The local logic of a system is a model of the regularities that support information flow within the system, as well as the exceptions to these regularities. The information channel is a model of the system of connections within the system that underwrite this information flow.

The model of information flow developed here draws on ideas from the approaches to information discussed in Lecture 1 and, in the end, can be seen as a theory that unifies these various apparently competing theories. The model also draws on ideas from classical logic and from recent work in computer science. The present lecture gives an informal overview of this framework.

Classifications and Infomorphisms

Fundamental to the notions of information channel and local logic are the notions of “classification” and “infomorphisms.” These terms may be unfamiliar, but the notions have been around in the literature for a long time.

Paying Attention to Particulars

We begin by introducing one of the distinctive features of the present approach, namely its “two-tier” nature, paying attention to both types and particulars.