"Christianity doesn't start with mental gymnastics, it starts with simple faith."
For many Christians, this is true, and it also is as far as they get - simple, blind, unthinking faith.
However, if you want to make any sense of the Bible (and what your pastor/minister preaches, as much of the time they merely pick pieces of verses out of the Bible to suit whatever message they want to deliver), you absolutely must include mental gymnastics. You have to:
- Reconcile how it is possible for God to love everyone, yet send unbelievers to Hell even though he doesn't WANT to, given that God has unlimited power to do anything and effect his will at all times.
- Rationalize what the difference is between a world without prayer, and a world where prayer often leads to an answer of "no you can't have your way."
- Explain away (usually through the all-encompassing Evil Atheist Conspiracy) the mountains of scientific evidence that contradict every aspect of the first ten chapters of Genesis.
- Explain why God needed four people to write the Gospel, and four conflicting accounts at that, when an all-powerful and all-knowing God should easily be capable of providing one coherent, non-conflicting book about one person's life and message.
- Defend the need to understand the Bible as "literal truth" while simultaneously holding the position that not everything in the Bible can be understood literally.
And that's just for starters.