What section of a textbook states the author purpose for writing book?

The section of a textbook that states the author's purpose for writing the book is typically called the Preface or Introduction.

Here's why:

* Preface: This section is often written directly by the author and provides a personal perspective on the book's creation. It might explain their motivation for writing the book, the intended audience, and the unique contributions it aims to make to the field.

* Introduction: This section can be written by the author or a different expert. It provides a more general overview of the book's topic, scope, and structure. It often includes a statement of purpose that outlines the book's main objectives.

While the preface and introduction are the most common places to find the author's purpose, it's also possible that the author's purpose is stated in:

* The book's title: A carefully chosen title can often hint at the author's intentions.

* The table of contents: The organization and structure of the book can reveal the author's focus and approach.

* The first chapter: Some authors choose to explicitly state their purpose in the opening chapter.

Ultimately, the best way to understand an author's purpose is to carefully read the book's introduction and preface, and to consider the overall context of the book.