With the remarkable advances in medicine, the lifespan of people and the death numbers are going way down. With increased childbirth, the Earth's population will continue to skyrocket. This is a major theme in that started this entire plot. Earth can only hold so many people.
This book has a major theme of corruption, Shusterman continually shows how easily people are corrupted and the very detrimental effect that it creates on society. It also shows how difficult it is to take down corruption, as it is almost always layers deep. It is displayed as a very human nature and the only way to avoid it is to live off of conscience.
Morality is discussed throughout the entire book, it is constantly shown how the lack of morality causes problems. It is important to know what you do is right, doesn't matter what you believe, right is right and wrong is wrong and people need to know the difference.