This book is simple but radical: rather than letting heresy writers define the story of "Simon Magus," it allows The Great Declaration (or Apophasis Megale) to lay the groundwork for Simon and Simonian thought. Building on this foundation, it adds details from other reports and stories about Simon, carefully filtering out the layers of slander and fiction. Simonian Christianity was real, and it evolved in different ways in different regions. The Great Declaration, a gnostic text likely written in Alexandria between 120 and 150 CE, reflects a different form of Simonian thought than what developed in mid-second century Rome and fourth-century Palestine. As our only secure Simonian source, it can serve as a baseline against which we can evaluate later heresiological claims about Simon (the Great Power), Helen (divine Wisdom or Thought), and their ancient followers (Simonians aka Helenians).