this is how i see it.,
1. They are chosen based on Gods foreknowledge, not randomly chosen.
2. God died for all.. Thus all are offered eternal life.
3. God knows every man before they are born, He knows their life from beginning to end.. He also knows their heart.
4. God chose to save them based on his knowledge before time began, so he knows everyone who will be saved by faith, and everyone who will reject him throughout all time (God is outside of time)
5. To say someone can be saved, then somehow lose it, is to say God made a mistake. Because it states God on one day granted a person eternal life. Sealed them with his spirit. Adopted them as his children, Justified them, Redeemed them, Made he who was dead in Christ alive in him, as well as many other things, some time later have to remove those things, because the person did something God did not already know he was going to do. (reject him)