It is easy to believe that we can always identify monsters by their grotesque appearances and distinctive physical abnormalities. In literature and film, however, it is evident that appearance is not always the primary indicator of monstrosity. Monsters are branded as such because of deplorable behavior such as animalistic urges and a general thirst for violence. When considered in this manner, however, the boundary between monsters and humans is not so clear cut. Although the vast majority of humans resist these urges, they nevertheless seem to be all too natural. In this paper I will explore what distinguishes monsters from humans. I attempt to define the borders of monstrosity in order to further understand common conceptions of human nature. I conduct my research by analyzing classic monsters in literature and film. I examine Adam in Mary Shelley’s Frankenstein, Grendel from Beowulf, and the replicants from Ridley Scott’s Blade Runner. I begin by applying Jeffrey Jerome Cohen’s method of identifying and classifying monsters (Monster Culture). I proceed by discussing the development of emotions and sentience in synthetic beings, which further stimulate a likeness to humanity. I then question whether modern depictions of monstrosity have evolved to reflect current times or remain in line with the classics. Although the monsters in discussion are deemed to be non-human creatures, I propose that the developed semblance of a soul is what allows them to encroach upon humanity. By juxtaposing this with the inhuman behavior exhibited by their human counterparts, I substantiate my thesis of the dual nature of monsters and humans. I continue to argue the implications this has on how we perceive and respond to the Other, as well as how it allows us to better comprehend the dynamics of racism, xenophobia, and other divisions in our communities.