Why theology is necessary?

Theology is necessary if you don't understand some aspect of sacred scripture. Studying the history and culture of Bible times, for instance, facilitates the understanding of Biblical texts. Knowing that the ownership of slaves was an accepted practice at the time The Bible was written helps to weigh the importance of the verses that recommend that slaves be obedient.

Verses that relate to meat given to idols and the subjection of women are other cases in point. You can't tackle a complex text like the Bible without some theology. The writers of each Bible book had their own, unique theologies as well. Grace vs. Works, War vs. Peace, Equality vs. Subjection of Women, Educated Pastors vs. Self-Appointed Pastors, and Rich vs. Poor are some of the opposing theologies found in the Bible.

I recommend you begin your study of Christian theology with Elaine Pagels, John Dominic Crossan, Bart Ehrman, and Randall McCraw Helms. google historical-critical method and Jesus Seminar. Check out Amazon.com under the heading Christian Theology or Bible Scholarship. There are endlessly fascinating writings in theology that enhance Biblical wisdom and foster religious unity. Theology rescues us from the medieval mindset by which Jews, heretics, nonbelievers, and "witches" were murdered by the millions.