Much more interesting are the arguments that explain why alien civilizations might exist, but be difficult to communicate with. Also, the section that argues aliens simply do not exist is also informative. Webb conscisely summarizes each argument, and then explains why it does not answer the paradox. For example, isn't it possible that advanced alien species can't be bothered with communicating other species? After all, we may be as simple as ants to them, and look at how poorly humans communicate with ants. Of course, says Webb, that is a valid argument - but in a galaxy full of alien civilizations, would you expect ALL advanced civilizations to make no attempt to communicate? Because if even one civilization is trying to be seen/found, then that ought to be enough for us to detect them. Webb covers SETI, the galatic habitable zone, the probability of life appearing on other planets, doomsday war machines, space travel, the Drake equation, and plenty more subjects. Each topic that he writes about is covered clearly, and quickly without being boring. The reader gets a tour of all the reasons why life on Earth might be unique, and the counterarguments as well. I really liked this book, it was informative and fun. The 50th solution is the one Webb believes to be true. I won't reveal it here, but he did a good job of convincing me that he is probably right.