What logic would lead you to that conclusion? Repeating an assertion is not a logical argument nor evidence nor proof.
Since we're interpreting things solely upon naturalistic grounds here (based upon the author's statement about the obvious character of nature), there aren't many possible conclusions that can be made
We all admit that things in nature at least sometimes don't work as the should, and in fact often go horribly wrong, as in the case of infant cancer. On purely naturalistic grounds, logic thus presents us with the following possibilities:
a. There is no designer(s)
b. There is an inept designer(s)
c. There is an insane designer(s)
Remember, the author is arguing that nature is obvious, so you can't appeal here to anything outside of nature.