Boyle argues that our ability for reflective self-knowledge is a byproduct of the "first person perspective" on our own lives that all human beings possess, as rational animals, and he seeks to defend this perspective against influential forms of skepticism about its soundness. Once we appreciate the connection between having a first person perspective on our own minds and having the capacity for self-knowledge, Boyle suggests, we can see a link between debates about how we know our own minds and the dark but intriguing idea that Jean-Paul Sartre expressed in his remark that, for a human being, "to exist is always to assume its being" in a way that implies "an understanding of human reality by itself."