Abstract The Human Genome Project (HGP), a 15-year study that began in 1990, expects to locate the 50,000 to 100,000 genes spanning our clmmasomes. According to many scientists, this effort will result in cures for genetic diseases. Yet throughout the course of genetic research, scientific findings have been surrounded by much uncertainty. Even when Watson and Crick announced the discovery of DNA, they acknowledged that their data mted on assumptions. How then do geneticists conduct research when strict proof is not always possible? When no one has directly observed DNA nucleotide sequeneces? Scientists often rely on probable reasoning to arrive at truth. In this essay, I examine discussions on the HGP through an Aristotelian lens to understand how rhetorical figures, such as metaphor and analogy, are wed as dialectical tooh to advance the frontiers of science.