Before we begin a systematic exposition of Theories of the Nature of the Builders (of which theories there appear to be at least one hundred and seventy-seven) it seems appropriate to provide what may be termed the Facts of the Builders. This is far easier than any enumeration of theories, since the facts are few in number: Fact 1: No living being, and no dead being whose word carries any semblance of validity, has ever seen or met a Builder. Fact 2: Various inorganic constructs possessing some form of intelligence have been found on, in, or in conjunction with objects created and left by the Builders. These constructs all claim to be of great antiquity. They also claim a full understanding of the Builder purposes in creating them. There are reasons to doubt the validity of all such testimonies, not least the fact that no two testimonies agree. Fact 3: The Builders made and left behind in the Orion Arm of the galaxy, and possibly in other galactic arms, a variety of constructions which are generally referred to as Builder Artifacts. More than a thousand of these are scattered around the Orion Arm alone. The purpose of many or most of them remains obscure. They range in size from a few meters, to lightyears across. The technology that went into their creation is beyond that achieved by any other species, living or dead, inhabiting these regions of our galaxy. Fact 4: There is no evidence that any Builder Artifact was constructed to be specifically inimical to organic life forms. Large numbers of deaths have been reported associated with different Builder Artifacts; however, in every case these deaths resulted from the unwise curiosity of beings seeking to explore, understand, or exploit the Artifacts. Fact 5: With one notable exception, every Builder Artifact was completed and set in position at least three million years ago. Any changes in Artifacts more recent than three million years appear to have been planned as part of their original design. Fact 6: Four years ago, there was unmistakable evidence of new, rapid, and unprecedented change in many if not all of the Builder Artifacts. Fact 7: At the same time, a completely new Artifact, named as Labyrinth by its discoverer Quintus Bloom, appeared near the star known as Jerome’s World. Fact 8: Soon after the appearance of Labyrinth, every other Artifact in the Orion Arm quickly vanished. Labyrinth itself was the last to disappear. Fact 9: Since the disappearance of Labyrinth, no evidence of any kind of Builder Artifact or Builder activity has been found in the Orion Arm. These, and these alone, are the facts concerning the Builders and the Builder Artifacts. We now proceed to the Theories themselves, which are legion.