Prof. Hernandez's monumental work The History of Central America covers everything about the region from the origin of the Mesoamerican period to the end of the Cold War. While the book has several informative maps and charts, many of the chapters spend less time describing facts and more time explaining Prof. Hernandez's theories. Indeed, the last two chapters consist exclusively of his exposition of theory of the role of Central America in post WWII world politics. Therefore, properly speaking, this book is not a history book.
Which of the following is an assumption that supports drawing the conclusion above from the reasons given for that conclusion?