Animals have been used in research aimed at improving human welfare for centuries, typically at the cost of their lives. This practice reflects the widespread belief that human lives are more valuable than non-human lives. People have different views about the ethics of animal testing and how it's conducted. But whatever your opinion, this scenario raises an important philosophical question: how do we determine the value of a life, whether human or non-human? One tool philosophers have used to consider this question is moral status. Beings with moral status should have their needs and interests taken into consideration by those making decisions that impact them. Traditionally, moral status has been seen as binary, either a being's interests matter for their own sake, or they don't. And historically, many philosophers believed that humans had moral status and other animals didn't. Some contemporary philosophers like Shelly Kagan have argued that moral status comes in degrees, but even in this model, he argues that people have the most moral status. However, determining what grants any degree of moral status can be difficult. Enlightenment philosopher Immanuel Kant thought humans have moral status because of their rational nature and ability to will their actions. A binary conception of moral status then suggests that beings with these capacities are "persons" bearing full moral status, while all other creatures are "things" without moral status. But thinkers like Christine Korsgaard have argued a Kantian view should include many non-human animals because of how they value their own good.