Well, That's what the whole thread is about up until now and there is not agreement on the subject :o)
I believe sin IS built in, but we do have a choice, and therein is the struggle.
Only grace, however, can change human nature, "If any man be in Christ Jesus he is a new creation, old things pass away, behold, all things become new."
I believe there is a "duality" or a "paradoxical paradigm" within which God operates in foreknowledge, calling, election etc.- all the while still leaving man a certain degree of sovereignty, within which man is learning about the nature of God and becoming transformed into it.
It is probably the minority opinion :o)
Since God causes "all things to work according to the counsel of His will" and " the creation was subjected to futility, not willingly, but because of Him who subjected it, in hope that the creation itself also will be set free from its slavery to corruption into the freedom of the glory of the children of God." He is absolutely sovereign .
Yet He, within His sovereign will can do whatever He wants, including giving man a measure of choice- a stewardship over which man may be penalized or rewarded according to his exercise of that stewardship, in order to gain friends(Abraham the Father of faith was called, 'the friend of God') who understand Him and can fellowship with Him intimately.
Is sin built in? Yes, "For, as by one man sin entered into the world, and death by sin; and so death passed upon all men, for that all have sinned"
Do we have a choice? Yes, "Walk in the spirit and you will not fulfill the lusts of the flesh".... "Draw near to God and He will draw near to you"
Can we do it on our own? Absolutely not, "For it is by grace you are saved through faith, and that not of yourselves, it is the gift of God".
Is there anything we can do to help ourselves and please Him? Absolutely. "Today, If you hear His voice, harden not your heart as they did in the wilderness and saw my works 40 years, as I said in my displeasure, 'They shall not enter my rest'"
Why? Because those who are in the flesh cannot please God, because they cannot receive the things of God and consider them foolishness.
How? Pray that you enter not into temptation....
Pray that you be "strengthened with might by His Spirit in your inner man"
Be not conformed to this world but be transformed by the renewing of your mind so that you can prove what is the good, the complete, the pleasing will of God.
That's just my