Longstanding debates on the ethics of animal experimentation have become only more complicated with the rise modern medicine. Mounting evidence suggests that many more animals than previously known possess a sense of self, the ability to reason, and a capacity to suffer. Given what scientists have learned about the expansive inner worlds of nonhuman animals, to what extent can they justify experimenting on them for the potential good of humans – especially when the subjects are some of our closest relatives in the animal kingdom? A collaboration between TED-Ed and the Parr Center for Ethics at the University of North Carolina at Chapel Hill, this animation frames the debate around the ongoing US government-funded research for improved smallpox vaccines, which uses monkeys as test subjects. From this starting point, the video traverses the views of philosophers across the centuries on the moral status of nonhuman animals, set against their potential worth for human benefit.