This book develops a novel account of the connections between justification, understanding and knowledge. It lays the foundation for a more systematic and interconnected treatment of these central notions in epistemology.The author's key move is to show first that a specific conception of doxastic justification constitutes our best point of entry into questions pertaining to a subject's ability to secure understanding of reality. Second, that the traditional order of analysis when it comes to the connection between understanding and knowledge should be reversed: knowledge itself is best conceived of in terms of a specific type of understanding.Rational Understanding will appeal to scholars and advanced students working in epistemology and philosophy of science.