My problem with free will (or the claim "I will") is its presupposition of "I" being the necessary condition for the act of willing. In actuality, "I" or the ego is composed of and dictated by a complex of competing unconscious wills. For example, the ego's will to eat is dictated by the unconscious will to hunger, the will to exercise is dictated by the will to health, and so on. In short, the ego is causally determined by the unfettered assertion of wills or natural laws. The ego can act in accordance with these wills (Schopenhauer described this as physical freedom) but it cannot be the necessary condition for them.
That's just my take on it. Some might cite this as evidence for an ultimate cause, i.e. God, but they'd run into the same problem I think.
