Lila: An Inquiry into Morals (1991) is the second book by Robert M. Pirsig, who is best known for his cult favorite, Zen and the Art of Motorcycle Maintenance. This semi-autobiographical story takes place in the autumn as the author is sailing his boat down the Hudson River. Phædrus, the author's alter ego, is jarred out of his solitary routine by an encounter with Lila, a straightforward but troubled woman who is nearing a mental breakdown.

As in his past book, the narrative is embedded between rounds of deep philosophical thought. The main goal of this book is to develop a complete metaphysical system based on his idea of Quality, introduced in his first book. (See Metaphysics of Quality) Unlike his previous book, in which he creates a dichotomy between Classical and Romantic Quality, this book is centered on the division of Quality into Static and Dynamic Patterns.

Another goal of this book is to critique the field of Anthropology. Pirsig claims its traditional Objectivity is ineffective. Pirsig turns his concept of Quality towards the goal of explaining some of the difficulties that our Western society has had in understanding the values and perspective of American Indians. One interesting conclusion he presents is that the Culture of the United States is the result of a melding of both Native American and European value systems.

Another theme he discusses using the Metaphysics of Quality, is the interaction between Intellectual and Social patterns. Pirsig states that until the Victorian era ended, social patterns dominated the conduct of members of our culture. In the aftermath of World War I, intellectual patterns and the scientific method were endowed with the responsibility for directing our goals and actions. The later occurrences of Fascism could be seen as anti-intellectual attempts to return social patterns to the position of domination. The Hippies could be seen as people who realized the flaws inherent in both social and intellectual patterns, and Pirsig thinks that this movement failed because it did not provide a more stable replacement, but rather degenerated into the lower level of biological patterns with its calls for Free love .