Fundamental to the perception of our place in the universe is to know whether Earth is the only planet supporting intelligent life. If the Earth’s intelligent life is truly alone, then it must be either an extraordinary occurrence or a unique consequence of evolution of the cosmos. On the other hand, if it is but one of a multitude of intelligent groups populating our Galaxy, then life on Earth may be part of a collection of great evolutionary diversity, and possibly not unique in its development and civilization. The problem is to determine whether or not life on Earth is alone.