Answer:
Authors make you think deeply by:
offering multiple viewpoints.
Explanation:
By doing that, authors provide you with different ways to view a single topic/issue. That is exactly what thinking deeply is all about: reflecting upon a certain topic in a broad way, without any restrictions or preconceived ideas, so the best conclusion(s) can be drawn. If you see only one side of an argument, that will limit your understanding and overall opinion of it.