Oliver O’Donovan, Resurrection and Moral Order, pp. 107-108:

“In saying that someone is free, we are saying something about the person himself and not about his circumstances.  Freedom is ‘potency’ rather than ‘possibility’.  External constraints may vastly limit our possibilities without touching our ‘freedom’ in this sense. Nothing could be more misleading that the popular philosophy that freedom is constituted by the absence of limits.  There is, to be sure, a truth which it intends to recognize, which is that the ‘potency’ of freedom requires ‘possibility’ as its object.  For freedom is exercised in the cancellation of all possibilities in a given situation by the decision to actualize one of them; if there were no possibilities, there could be no room for freedom. Nevertheless, there do not have to be many.  Even in deciding whether we will accept an inevitable situation cheerfully or resentfully, we exercise our freedom in choosing between alternative possibilities of conduct.  Where the popular philosophy becomes so misleading is in its suggestion that we can maximize freedom by multiplying the number of possibilities open to us.  For if possibilities are to be meaningful for free choice, they must be well-defined by structures of limit.  The indefinite multiplication of options can only have the effect of taking the determination of the future out of the  competence of choice, and so out of the category of meaningful possibility for freedom.  For example, a decision to marry depends upon marriage becoming possible within the limiting structure of one’s existing relationships.  If that limiting structure were withdrawn, and one had all the conceivable partners in the world immediately available, one could not freely choose to marry any of them.  The empty space for freedom must be defined if one is to move into it.  Furthermore, the decision to marry itself cancels out both marriage and singleness as possibilities, by actualizing marriage as a new limit to which one has bound oneself.  The empty space must be cancelled when one does move into it.  Decision depends upon existing limits and imposes new ones.  When the Holy Spirit makes a person free, that freedom is immediately demonstrated in self-binding to the service of others: ‘You were called to freedom . . . In love be one another’s slaves!’ (Gal. 5:13)”