We agree with you completely. But please do not read chapter 7 out of context. The book is a complete story that is being built successively. Encapsulated state and what you call polymorphism are actually covered, but not in this chapter. In fact inheritance creates more complication in the sense that makes necessary the introduction of many other concepts that is being covered in this chapter (Chapter 7). Encapsulated state is all over the book. In particular Chapter 5 already introduces a simple concurrent form of objects that communicate with 'real' message sending. Chapter 6 talks about encapsulated explicit state and many ways to build such entities. In chapter 7 we constrast the functional view to the object-oriented view which really implies pholymorphism in the sense that related categories of objects accepts the same message but execute it in its specialled way. This is contrast to the case-analysis on type that has to be done in the functional view. Still all of these things are minor things in our book. The intension is a firm understanding and the relationship between different programming models, and Finally we have an extensive treatment of concurrent and distributed programming models (Chapters 4, 5, part of 7 on active objects, 8, and the chapter 11 on distributed programming) All these are done with working programs and no handwaving. --- Seif