First published in 1986, this book starts from the premise that Blake's poem Jerusalem is in effect his defence of human imagination. The formal categories are literary but the aim is the philosophical one of Creating a System. The philosophic meaning emerges from the structure since its form is that of an epic poem. The argument proceeds plate by plate and topologically within each plate of the illuminated text, but does not aim to answer every last question about Jerusalem - only to show how the system is created. The author demonstrates how Blake interprets, modifies, and incorporates certain principles and their consequences to fashion an epic in which he opposes the prevailing aesthetic system and constructs his own.