—Therefore, without depriving you of your free choice, someone who knew you totally, better even than you know yourself, could know what your choice was going to be, because it would be an elementary deduction from who you are.—
I agree: and I think it gets weirder than I that. People who study the brain have some experience with using electrodes to stimulate the nervous system, inducing things like movement. But the really startling thing is that it is not only the movement which is sometimes produced by the stimulation: but also the experience of deciding to move. In such a situation, how do we characterize what’s going on?
I think that in this context, we are apt to say “but, we are not really free, because we are being forced to decide, even though we don’t necessarily know it.” But there is a possible response to that: in all other situations of forcing, the forcing is of an external constraint on our own choices. But here, someone seem to have tapped INTO our system of making choices. In this situation, it actually seems to make sense to say both that our choice was determined by someone else but also at the same time was our own choice. And in a certain sense, this is a question of degree, not kind, from what people do normally when they, for instance, exploit what they know about our character to manipulate us into making choices that they can predict.
So, if you accept the above formulation, an omnipotent/omniscient being could not only predict our choices, but (since it can presumably direct all things, to an even greater extent than doctors with electrodes) direct them without them ceasing to be our choices.