We humans have free will, we must choose, and bear the responsibility for that choice. What are the fateful alternatives of that 9 choice? These are presented in subsequent verses. That is the doctrine of Good and Evil. For Zarathushtra, Good and Evil existed as such, and each one of us had to choose the good or the evil alternative in every situation in life. Good is chosen by the clarity of our recognition of the Truth and our innate Rightmindedness. Evil, since it is action contrary to the Ideal Truth, is chosen because one is in a state of deception; and evil is destructive of the Righteous Order in this world, a world which ought to evolve to perfection. Evil ultimately will perish. The righteous will achieve the state of Best Consciousness through their right choices, and the opposite will be the state of the evil-doers.

We do have Free Will. This is The Highest Law of Ethical Law and Natural Order laid down by Mother Nature. For without Free Will, we lose Consent. And without Consent, we have no Freedom and thus we would be Slaves. 

And then, Evil would triumph. The first Law of Nature is Free Will to preserve our Self-Authority — The 2nd Ethic — or else, we would be born enslaved and without Hope. Thus, Consumption would devour us and all would end. 

Free Will does exist and is mandatory for our Preservation and Freedom.

You must choose Ignorance (Not Love, Evil, and Lie) or Knowledge (Love, Good, and Truth).

Free Will is required.