What is the role of the soul in human life?

St. Cyril of Jerusalem says, “Know also that you have a self-governed soul, the noblest work of God, made after the image of its Creator: immortal because of God who gives it immortality; a living being, rational, imperishable, because of Him who bestowed these gifts: having free power to do what it wills.⁴⁶⁴ For it is not according to your birth date that you sin, nor is it by the power of chance that you commit fornication, nor, as some idly say, do the conjunctions of the stars compel you to give yourself to wantonness.⁴⁶⁵ ”⁴⁶⁶