This volume comprises three important texts of the Yogacara school.
Demonstration of Consciousness Only is a translation of Vasubandhu's "Thirty Verses" plus the interpretation of Dharmapala as the ultimately correct view of the text, with the supplementation of two or three divergent interpretations. It is an attempt to answer the question of the mechanism and nature of ignorance by demonstrating that seemingly real external objects of perception and the equally seemingly real self who perceives these things are mental fabrications that do not exist apart from consciousness itself.
Thirty Verses on Consciousness Only is the short verse work by Bodhisattva Vasubandhu that propounds the idea that nothing exists except consciousness or mind, and that all things believed ty the ordinary person to be objective realities outside mind are in reality mere mental constructs.
The Treatise in Twenty Verses on Consciousness Onlyis a companion piece to the Thirty Verses. It is a series of hypothetical objections by possible opponents with replies by Vasubandhu. The objections of opponent takes the realistic, no-nonsense position that the things seen, heard, smelled, etc., are real things that exist in the world outside the mind. The opponent typically offers an argument as to why it cannot be possible for perceived objects to be merely mental constructs. Vasubandhu counters each argument, explaining why the realistic argument is faulty, and why objects of perception cannot rationally be considered to exist apart from consciousness.