Outside belief, I wonder how people could be absolutely certain about something which needs forever to prove, like polemic between the concept of 'free will' against 'predestination' amongst the scholars.

If you believe in predestination, then there is no reason to regret anything. If you believe in free-will, then there is no reason to acknowledge the prophecy. If you believe in both, then you are just looking for an easier way to perceive reality. If you don't believe in both, then you may have an eccentric way of understanding life.

People, come and go. The truth, stays. In between both, so many beliefs.

Human willingness to believe precedes their ability to think.

If there was no free will in men, then there is no sins. When sins happened, it was 'free will' that made them doable. This is true, unless God has predestined human to do and to have sins.

Not all can believe anything they want to,
because not all have the ability to believe.