Silent Illumination is one of Chan Buddhism's core methods, simultaneous combining the twin practices of śamathā (calm abiding) and vipaśyanā (clear awareness). Unlike meditation on the breath, Silent Illumination is a "sudden" method, because using it means direct use of our true, free nature rather than a preliminary practice to get closer to that nature. Silent Illumination has deeply influenced related methods in other traditions of Buddhism, such as shikantaza or "just sitting" from Sōtō Zen. 

Guo Gu draws upon his deep experience with this method to explain exactly what the "methodless method" entails, how to enter into this practice, and its connection to our everyday life.