As we can tell from the title, Alone in the Universe, the author’s standpoint is that Earth is the only planet that host’s life in the universe. Within the book, John Gribbin backs up this claim with theories, statistics, facts, and equations. There are multiple purposes of this book.
In the beginning of the book, Gribbin provides descriptions and facts. He explains the commonality of planets and stars as well as informing the reader on the expanse of human knowledge on space. In the second chapter is when Gribbin transitions more into a persuasive tone, but remains informal. Multiple equations and theories are explained that, if correct, would imply that it is nearly impossible for there to be other life in the universe, which is his claim. The rest of the book remains in like this, with the author backing up his claim.
Overall, the purpose of this book is to inform as well as persuade. It informs of all the equations and statistics there are to know about the chances of other life in the universe. The book is also argumentative because Gribbin backs up his claim and tries to convince the reader that his claim is true.