Free will and determinism

To return to the primary topic of this thread, I have encountered what I consider to be one of the best arguments for free will, a philosophical argument hinging on the concept of coherence, courtesy of poster Origenes on Uncommon Descent:

To say that a person is not free is to say that he is determined by something beyond his control. If a person is determined by something beyond his control, he does not control himself. If a person does not control himself, he also does not control his thoughts.
A person who does not control his thoughts is not a rational being. Something that is not a rational being has no place in a rational discussion about free will. No one can coherently argue that he is not in control of his thoughts.
For the sake of coherency, those who search for the truth and engage in rational inquiry must reject the possibility that free will does not exist.

Any comments on this, like plausible refutations?
 s