Free will is basically the feeling of experiencing a mind that operates in a certain way. Just because you don't know what the requirements are doesn't mean it doesn't exist. You could just as well say "love doesn't exist" because physicists don't have a great model of what causes it.
Sure free will exists; it just isn't a objective natural phenomena to be studied under the domain of physics. It's an emotion. It's what happens when you brain builds counterfactual models of its own behavior. It's really no different from things like pride and regret -- you experience them only because you can imagine a reality different from the one you are in. There needn't be any physical mechanism for predicting the construction of those realities.
I think this is a perfect example of a pseudo scientific article. The author claims there is no free will based on another claim : "laws of Physics can describe/predict human actions". Physics does not make this second claim, at least, not yet.
The Aristotelian treatment of causality is what's needed here. Objects act in accordance to their nature. Cause and effect is the course of how objects interact with each other. For a given situation, objects A & B will produce the same results if made to interact with each other in a given way.
This is in contrast to the Humean treatment of causality, which is a listing of events where objects play a nominal role.
Let's consider the case of a person considering an argument for determinism. The arguer is presenting a logical sequence of statements building to a conclusion. The considerer is having to focus on each of the presented facts and how they relate to the conclusion. It is this act of focusing which is the core role of volition. The arguer is counting on the focusing act to take place in order to present an argument for determinism. It may be argued that volition can't be proven, but in order to argue against it, it's necessary to rely on volition still the same. Funny thing, volition.
Determinism should be the obvious starting point for both physicists and philosophers. The idea that any action or set of events can unfold outside of prior physical causes underlies the idea of free will, but it also essentially contradicts the law of causality: every event has an exact set of causes, prior conditions which map perfectly to the resulting effects of a given system. The claim that your actions are purely the result of your own decisions does not factor your thinking itself as being a fundamentally physical process, governed only by physics. Thinking is a natural process, founded on top of other natural processes, and bound ultimately by the greater forces of causality. Of course, quantum randomness on a fundamental level may alter the effects of these processes such that the future cannot be predicted, but it does not dispute the fundamentally physical, and thus causal, nature of thought.
If thought is merely chemical gears spinning, doesn't that remove any kind of control or responsibility of the person for their actions? It would be morally wrong to punish someone for an act they had no control over for example.
Just as space is what gives matter room to exist, probability is what gives information room to exist. In this unfolding of probability to information, there is a possibility for choice to exist.
Sure free will exists; it just isn't a objective natural phenomena to be studied under the domain of physics. It's an emotion. It's what happens when you brain builds counterfactual models of its own behavior. It's really no different from things like pride and regret -- you experience them only because you can imagine a reality different from the one you are in. There needn't be any physical mechanism for predicting the construction of those realities.