In its early days, Christianity was not a very unified or established movement. Groups within the movement opposed one another and many followers had highly varied ideas on theological matters. Christian thinkers were only beginning to develop solid opinions and theories that would become part of Christian belief. The evolution of such ideas is apparent when reading scripture from a historical perspective. When the letters of Paul are studied with their chronology in mind, it is easy to see the way that his eschatological theories and teachings developed and changed.
This is especially apparent in the letters of 1 Thessalonians, 1 Corinthians, and Philippians. Over the course of the writings of these letters, we see Paul attempting to develop an understanding of the end of days. The view of this end of days, or Parousia, differs greatly from one letter to the next most prominently in temporal aspects. There is a discrepancy among the letters in regards to the time and nature of the Parousia of which Paul speaks. However, when viewed and considered in context of one another, we see more of a logical evolution and gain a sense that Paul is developing a deeper understanding as he writes.
In 1 Thessalonians, Paul writes of the Parousia as an event that will take place at a definite place in time. He describes it as something that will come as a “thief in the night” (1 Thess 5:2). He uses the symbolism of a woman in labor, whose pains come upon her suddenly and without warning. Paul also emphasizes the importance of staying faithful and living moral lives. He advises readers to “keep awake and be sober” (1 Thess 6), for he believes that the day of the Lord will happen suddenly and in the near future and that believers must be prepared.