This is a good point and essential to understanding our freedom. It seems that there is a necessarily rational component, if not to freedom per se, at least with the type of freedom an all-good God would grant or ultimately give his creatures. (For a freedom which only included exercising actions the consequences of which were unpredictable or in a context which was not truly reflective of reality would be a curse, not a gift, and would only be given by an evil being.)
Yet I do think freedom is real, and that we are in truth actually in situations like the schizophrenic described above. The question then becomes this. For what purpose is this type of freedom, which seems so different than a “pure” freedom which makes it, as Lewis says, “not really possible to do otherwise” - for what reason is this different kind of freedom given to us? I suspect it has something to do with the making of our individuality and separateness from God, a necessary condition for our ultimate unity with him. Does this make sin inevitable? Can it be that sin (and therefore death?) is a free yet nevertheless unavoidable consequence of being a separate being from God, exercising an independence and existence of one’s own?
Also of interest are some other thoughts of Lewis on freedom.
"I would say that the most deeply compelled action is also the freest action. By that I mean, no part of you is outside the action. It is a paradox. I expressed it in Surprised by Joy by saying that I chose, yet it really did not seem possible to do the opposite.”
He said the above in his “last” interview.
“All that Calvinist question - Free Will and Predestination, is to my mind undiscussable, insoluble. Of course (say us) if a man repents God will accept him. Ah yes, (say they) but the fact of his repenting show that God has already moved him to do so. This at any rate leaves us with the fact that in any concrete case the question never arrives as a practical one. But I suspect it is really a meaningless question. The difference between Freedom and Necessity is fairly clear on the bodily level: we know the difference between making our teeth chatter on purpose and just finding them chattering with col. It begins to be less clear when we talk of human love (leaving out the erotic kind.) “Do I like him because I choose or because I must?” - there are cases where this has an answer, but others where it seems to me to mean nothing. When we carry it up to relations between God and Man, has the distinction perhaps become nonsensical? After all, when we are most free, it is only with a freedom God has given us: and when our will is most influenced by Grace, it is still our will. And if what our will does is not “voluntary” and if “voluntary” does not mean “free” what are we talking about?”
Letters Vol. 3.
“The whole struggle was over, and yet there seemed to have been no moment of victory. You might say, if you liked, that the power of choice had been simply set aside and an inflexible destiny substituted for it. On the other hand, you might say he had been delivered from the rhetoric of his passions and had emerged in unassailable freedom. Ransom could not for the life of him, see any difference between these two statements. Predestination and freedom were apparently identical. He could no longer see any meaning in the many arguments he had heart on the subject.”
Perelandra