Free will is not merely the ability to choose between good and evil: for that is merely freedom of choice, which every man possesses. But the man whose will is truly free is able to choose between multiple goods, and also become learned in discerning the most virtuous.
For choice, being an external impersonal principle, has no personal moral quality; whereas the will which performs the choosing is indeed held accountable, as it is a faculty of persons. The heart of this matter lies in the allegiance of the will, not in whether or not men are freely allowed to choose – for indeed they all are. The will is swayed much by the desire of the soul; so that the more sanctified the soul, the less it considers evil to even be a viable option, and the more goods from the providential hand of God are then opened to its discretion.
Therefore, the most perfectly free will would be that which beholds both good and evil, but chooses that which is only good. Or, to cast this as the choice in the garden according to philosophical terms: the most perfectly free wil chooses the Tree of Life over the Tree of False Dialectics; the latter being “knowledge, falsely so-called”.
Men come to Christ on their part by choice; but they remain obedient in Him on their part by the freeing of the will from sinful desire, through the renewing of their mind according to His Word, which teaches them every good thing, communicating to them the very Life of God.