Free will changed after the sin of the tree of knowledge. Beforehand, we did not have any inner inclination toward evil; rather, evil needed to entice us from the outside. But after the sin, good and evil mingled within us, and free will became a struggle between one’s inner inclination toward good and one’s inner inclination toward evil.

Before the sin of the first man, evil existed only outside of the human being:

Before the sin, the first man certainly had free will and could incline himself whichever way he desired, whether to do good or the opposite, God forbid, for this was the intention of creation. Moreover, this is apparent because he sinned. However, his free will was not due to the fact that there were forces of evil within him, for he was entirely righteous, and was composed only of forces of holiness. Everything in him was righteous, holy, and pure, absolute good, without any trace of the opposite. The forces of evil were a separate entity and external to him. He had free will, and he could enter into the realm of the forces of evil, God forbid, just like one may choose to walk into a fire. Therefore, when the “other side” wanted to cause him to sin, the snake needed to come from the outside to entice him.

Today, good and evil are intermingled, both in people and in the different dimensions of existence:

In contrast, nowadays, the evil inclination that entices an individual is within that individual. It seems to the individual that it is he himself who desires and is drawn to do the sin, and not that something outside of himself is enticing him…. This is the meaning of “the tree of the knowledge of good and evil” (Genesis 2:9); good and evil joined and became mixed together, one inside of the other, within [the individual] and dimensions of existence. [Consumption of the fruit of the tree brought this about] as the meaning of knowledge is connection. (Rabbi Ĥayyim of Volozhin, Nefesh HaĤayyim 1:6)