Darwin

"It is, no doubt, extremely difficult even to conjecture by what gradations many structures have been perfected, more especially amongst broken and failing groups of organic beings..there are, it must be admitted, cases of speical difficulty on the theory of natural selection;"

Darwin discusses in his Recapitulation and Conclusion how he's expecting people to criticize his theory of evolution. He summarizes his argument and then acknowledges the other side of the argument to address his thoughts more clearly. Darwin is aware of the criticism and demonstrates his view through rhetoric to emphasize his point strongly. Also, throughout the final chapter of his book, he uses examples to argue his point and then backs up these points by using his own logic.