How can one understand that someone who can make mistakes can still know something? This problem, as the central thesis of this book states, cannot be solved as long as one adheres to the dogma of epistemology, which holds that the concept of knowledge is an analytical unity of elements whose concepts are more fundamental than the concept of knowledge itself. Andrea Kern proposes an alternative concept of knowledge, centered around a systematically developed notion of rational capacity based on Aristotle, Kant, and Wittgenstein. When knowledge is understood as an act of rational cognitive ability in this sense, which a thinking subject possesses as such, it can also explain how one can make mistakes and still know something.