The bottom line: A book full of reasonable and rational arguments that equips Christians to intelligently defend what they believe.
On Guard does two things very well: (1) Prepare Christians with mature, well-developed arguments that properly defend the existence of God (2) Educate Christians who have never seriously thought about some of the peripheral philosophical and existential questions surrounding their faith.
In the end, On Guard succeeds in making you feel confident about your beliefs and thus eager to engage others. As Craig excels in explaining, Christianity is not based on “blind faith” but makes perfect rational and logical sense in the world in which we all live.
The book is roughly divided into three parts: the first two sections tend to work outside of the Bible and detail arguments for the existence of God from the stance of reason and philosophy. Here, Craig searches for answers to existential questions (e.g. Why does anything exist? Why did the universe begin? What about suffering?). These questions weigh evidence and tend to rely on science and logic alone. The final part works from within the Bible and provides historical and academic defenses for some of the Bible’s central truth claims including the existence of a historical Jesus and evidences of the resurrection.
In the first two parts of On Guard, the author makes his arguments by analyzing premises that support a conclusion. While this makes perfect logical sense, everyday people tend not to converse this way so a reader may afterwards find themselves unloading the arguments and breaking them down in more relatable ways. In a more formal academic debate, however, the way these arguments are presented may work perfectly. And from a personal standpoint, in a few instances the author will veer off into theology and make some claims that are debatable. Neither of these reservations take away from the power of the central thrust of the book.