I also appreciated the distinction made in this book between:
Bateson, Keeny, and many other illuminati of systems theory have completely missed this difference, which is quite significant and useful in tracking how a person responds in a given situation, and also as a guide to changing that response.
Changing scope is the basis for context reframing, which changes the kind and amount of sensory information in someones representation. Expanding scope is sometimes called seeing the big picture. Change of scope is the underlying basis for a number of the content reframing or sleight of mouth patterns (justification, consequences, etc.)
In contrast, a category is a group or set of experiences. When someone thinks of a category, they focus on the criteria used for creating the category, and tend to ignore most of the sensory-based information in the individual experiences in the group. This is the difference between FA (perception of a specific dog) and the f2 category dog. The category typically elicits a representation of an average or generic dog, rather than a specific dog. Categories provide the underlying basis for a different set of content reframing patterns, such as redescription, model of the world, apply to self, etc.
Charles Faulkner and I have been exploring the many ramifications of this important distinction between scope and category for the last couple of years. We continue to find uses for it, and have been teaching what we have learned so far in a seminar titled Changing Levels of Meaning and Experience.