I can't tell you how many times I've heard non-Christians and Christians alike complaining about how confusing the Bible is and how it contradicts itself. I decided to try to shed a light on why there are so many differing opinions out there, why (in a belief system that is supposed to be about unity) there are so many different "Christian" theological ideas and why people see contradictions where there aren't any.
Sound like an impossible task? Believe it or not, it all is explained, actually, in one verse: (I Corinthians 2:14) "The man without the Spirit does not accept the things that come from the Spirit of God, for they are foolishness to him, and he cannot understand them, because they are spiritually discerned." Did you get that? Where does spiritual truth come from? The Spirit of God alone.
(If, of course, you don't believe in God or in the Bible, consider this idea philosophically: If there were a God and He wanted us to come to love Him and know Him better, wouldn't He want to be intimately involved in that process? The Bible tells of a God Who works in just this manner--a characteristic that is also mirrored in how Jesus taught--through parables. The Bible teaches us that learning about God and spiritual matters is a two-way street. God doesn't force unwanted beliefs on us. He desires that we want to know Him.)
The Bible is full of spiritual truth, but it is not like any other book we will ever study. You can spend your entire life studying the Bible and never get it. It isn't like a mathematics textbook--something that, if you spend enough time and energy studying it, eventually it will make sense. No. The message and the wisdom in the Bible can only be revealed by the Spirit of God. No matter how hard we try to get it, we won't, unless God reveals it to us.
So, how do we ever understand? We ask Him to show us. We ask for Him to reveal His truth to us.
"Ask and it will be given to you; seek and you will find; knock and the door will be opened to you. For everyone who asks receiveds; he who seeks finds; and to him who knocks, the door will be opened." Mathew 7:7-8
So, how do we understand what the Bible is saying to us? We ask God to reveal it to us. How do we reconcile the "contradictions" in the Bible? We ask God to show us the passages in the Bible that will make its full meaning clear, and we keep reading, digging and searching while being open to His teaching. Why are there so many different theological sects out there? Because not everyone is open to the Spirit's leading to the same degree, too many people ignore the part of the Bible that says to avoid meaningless arguments (2 Timothy 2:23) and too many of us have allowed our focus to shift from Christ to politics, popular culture & lies.
The question you should ask yourself is this: are you honestly asking God to reveal Himself to you? And, when He does answer, will you be open to His Spirit? Will you allow yourself to learn what He has to say, or will you rely on your own limited ideas about what "He must be like"? Remember, God cannot be put into a box. He is not subject to human limitations, rules or expectations. God defines Himself. But, if you listen, He'll tell you Who He is.