How do we know that chosen people cannot finally fall?

The assurance that God's chosen people cannot finally fall is rooted in the doctrine of perseverance of the saints, which is affirmed in various passages of Scripture. For instance, in Romans 8:30, we read that those whom God predestined are also called, justified, and glorified, indicating a complete and unfailing work of God from beginning to end. True believers, being kept by the power of God, will not fall away but will demonstrate their election through their endurance in faith and obedience, thus fulfilling God's promise.