Eschatology is the study of the end of life, the end of time, and the Final Coming of Christ. In Eschatology, Christian Theology focuses primarily on the "Four Last Things" that comprise its study. They are Death, Judgment, Heaven, and Hell. In addition to these areas, Mr. Plese explores as part of the five-part series on these topics, Purgatory, the place of temporary purification after death for souls that die in the state of grace (i.e. are destined for Heaven) but are not yet perfect and able to enter Heaven.