Darwin had many arguments on why his theory was correct, but gaps were also present. A few of the principles within his theory included variation in nature, natural selection (pg. 492), and competition between species. Darwin was fathomed by the fact that other naturalist didn’t agree with his theory. This had something to do with others not being able to comprehend his ideas and theories because they were so different. Darwin blamed stubbornness on others rejection to his theory (pg. 488). Darwin highlighted that all living species are part of a chain of decent. Darwin ultimately argued that his theory will be used in understanding the natural world further.
I think his most convincing argument was his on the process of natural selection. Natural selection works slowly but only in few steps. Natural selection works in part with competition (pg. 493). In both competition and natural selection species ultimately fight for their right to live. Be that either in the form of inhabiting a place or simply capitalizing on food or prey before its competitors. This really brings the whole phrase the early bird gets the worm full circle in the sense that in natural selection the early bird would survive and the late one may not. Darwin used the example of upland geese not having webbed feet because they are rarely swimming. This is the most convincing argument to me because I have witnessed natural selection take place in the form of a wolf pack attacking an ill old elk in Yellowstone National Park.