There is ample evidence from psychology and cognitive science that a person's beliefs, memories, expectations, concepts, and desires can influence how that person perceives the world. In other words, the way an object looks (the color, size, shape, etc.) to a person can vary according to his or her beliefs, memories, desires, and so on. But a person is principally justified in his or her beliefs about the world by how things look to that person. So, if how things look to a person justifies that person's beliefs about the world, and that person's prior beliefs, memories, and desires influence how things look, then his or her prior beliefs, memories, and desires influence the justification for his or her beliefs about the world. This influence creates several significant philosophical problems. In this dissertation, I introduce and attempt to solve these problems by constructing a theory of justification in which a person's beliefs about the world are justified if and only if his or her prior beliefs, memories, and desires constitute a coherent worldview.