Basil Answers Mackie

“But why did we not have sinlessness in our structure, one may ask, so that the will to sin would not exist in us? Because indeed it is not when your household slaves are in bonds that you consider them well disposed, but when you seem them willingly fulfill your wishes. Accordingly, God does not love what is constrained but what is accomplished out of virtue. And virtue comes into being out of free choice and not out of constraint. But free choice depends on what is up to us. And what is up to us is self determined. Accordingly, the one who finds fault with the Creator for not fashioning us by nature sinless is no different from one who prefers the nonrational nature to the rational, and what lacks motion and impulse to what has free choice and activity.

St. Basil the Great, Homily Explaining that God is Not the Cause of Evil, 74.