Human sacrifice, defined as the killing of humans or the use of the flesh, blood, or bones of the human body for ritual purposes, has been a widespread and complex phenomenon throughout history. Most contemporary scholars try to explain human sacrifice in terms of earlier theories of sacrifice in general. Though the explanations given for the purposes of sacrifice have been almost as varied as the phenomena themselves, they may be reduced to nine common themes drawn from four of the classic works on sacrifice. These themes may be illustrated with descriptions of human sacrificial practices in differing cultural contexts.

E. B. Tylor (1832–1917) theorized that the origin of religion lay in the primitive tendency to "animate" the entire world with "soul-ghosts." Human sacrifice released these soul-ghosts so that they might join their ancestors and function as a gift to gain particular ends, as homage to a...