Specializing in classical American philosophy, Mustain completed her master's and doctoral studies at Southern Illinois University. Her research and teaching interests include American philosophy, philosophy of education, feminist theory, and philosophy of medicine. Her recent book, Overcoming Cynicism: William James and the Metaphysics of Engagement, addresses the problem of contemporary public cynicism through the work of American philosopher William James. In 2011, she received the St. Mary's Distinguished Faculty Award in recognition of teaching excellence. In 2012, she and Dr. Glenn Hughes received a National Endowment for the Humanities "Enduring Questions" grant for development of a course on human dignity.