Early Mahāyāna teachings systematically mapped the mind and its behaviors. The most rigorous of these mappings comes from the Yogācāra school of thought, sometimes translated as "Consciousness-Only" or "Mind-Only." 

According to Yogācāra philosophy, all of our experience of the world is mediated by the mind. Thus, by understanding how the mind works to create emotions and subjective experience, we can come to a more objective view of ourselves, our thoughts, and our feelings. The Yogācāra philosophical tradition dissected the physical and mental worlds into 100 basic components. Of these, 51 are the components that make up the activity of the mind, known as "mental factors."

The Yogācāra typology of the mind underlies much of later Mahāyāna doctrine and practice, including Chan and Zen Buddhism. However, it is rare to find a thorough introduction and analysis of the 51 mental factors outside of abstract philosophical texts, which are thorough but disconnected from meditative methods and practice. 

Guo Gu offered this series of lectures in 2016 based on the teachings of his teacher, Master Shengyan, with the aim of introducing this important philosophy without straying from its implications for our practice and everyday lives. In this course, Guo Gu introduces all 51 of these mental states, virtuous and unvirtuous, skillful and unskillful, and analyzes their impact on our practice, including how to recognize and counter harmful mental states.

Ultimately, this teaching shows us how to live our lives unburdened by strong and sometimes uncontrollable emotions, returning to the basic freedom of Chan.