The most obvious theme of the novel is the necessity for the human mind to use technology to solve humankind’s problems. Neither the scientists with their human mistakes nor the machines with their mechanical problems are able alone to find the source of the disease; neither alone can cure it. Moreover, both parties are fallible: Human error—a misspelling—causes one prospective member of the team to be notified too late to participate; machines are not entirely dependable either—a stray piece of paper clogs a teletypewriter, preventing an important message from being received. When man and machine join together, however, the scientists are free to use their intuition while the machines shorten the hours which it takes to do the innumerable computations needed to solve the puzzle of the bacteria from space.
The novel offers a fascinating glimpse into the world of scientific research and manages to teach much about microbiology in the course of telling a fast-paced adventure. Crichton himself worked at the Salk Institute after receiving his M.D. degree from Harvard University, and his technical competence informs the novel. The reader learns about genetics, studies the treatment of infectious diseases, reads of the history of bacteriology, and discovers some of what is known about the ability of bacteria to survive and multiply in a hostile environment. In addition, the reader comes to see the world as a place filled with bacteria, ninety-seven percent of which are helpful and necessary to humankind. The most pointed example of the book is the human body, which is covered and filled with bacteria: Its complete “cleansing” is neither possible nor desirable, for to sterilize it would be to kill it.
One theme notable by its absence is any moral judgment on the action of the government in lying to the scientists about the purpose of the research on which they are engaged. The plot is not so much resolved as stopped: The bacteria magically become harmless, all the survivors recover, and the scientists return to their lives, apparently unchanged or unenlightened by the events.