Kreeft delves into the essence of what angels are made of, drawing from biblical and theological sources. He explains that angels are purely spiritual beings without physical bodies, created by God to serve as messengers and servants. This idea challenges common misconceptions and provides a deeper understanding of their role in the divine order.

The book explores how angels interact with both God and humans. Kreeft discusses the ways in which angels convey God's messages to people and how they assist in guiding and protecting individuals. This theme highlights the importance of angels in the spiritual lives of believers and their ongoing presence in the world.

Kreeft addresses the reality of demons, or evil spirits, and their influence on the world. He separates fact from fiction, providing a clear and reasoned explanation of their origins, nature, and activities. This theme is crucial for understanding the spiritual battle between good and evil and the significance of spiritual vigilance and protection.