As biologists have recognized since Aristotle, there are two complementary ways of looking at organisms: one can think of them from the viewpoint of homology, asking about the isomorphisms between different organisms and even within the organisms themselves; or one can think of them from the viewpoint of adaptation or final cause, asking about the ends that the features serve. I look at this divide with special respect to the theory of evolution through natural selection as first announced by the English naturalist Charles Darwin in his "Origin of Species" in 1859, considering both different interpretations that scholars today make of Darwin's work and the overall implications of Darwin's achievements for the homology/adaptation, often called the "form/function," divide. In this essay, I draw on some of my previous work, including Ruse 1998, 1999a, b, 2000, 2003, 2004, 2005a, 2006, 2007, 2009.