Hi Paul and all,
wow, I think there are much, much more aspects to consider regarding the issue of "free will" than were mentioned or examined in the article by Sean Carroll. I like to mention some of these aspects here.
First of all, there are fundamental, "primitive" needs for any living human subject, at least until that subject is more or less an adult. For example these are food, water, a shelter against rough environments, care from other humans. These are the "hard physical" needs that increase the chances of survival even - and especially - for newborn babies, but also for adults.
Then there are other needs, such as security, love, care, being accepted, being recognized and valued. Additional needs may be our striving for "happiness", "fun" and "playing", or in other words to be creative, to create something - even if it is just creating food for some animals out of what one had planted on the field or to create something just for the purpose of fun (the rules of a chess game, baseball game etc.).
Now, for each and every of these mentioned needs there can be specified some exceptions:
The homeless person who doesn't want to live again in a conventional home / shelter. The subject who committed a hunger strike. The other subject who deliberately committed suicide (maybe by a hunger strike, but surely also via other measures). And there may be persons who do not need, for whatever reasons, "things" like love and being valued, for example some psychopaths ore else.
When talking about "normal" people, we take it for guaranteed that they regularly have the "will" to eat during their living. That they do not kill themselves. That they like to be happy as much as possible (in opposition to being grumpy as much as possible). That they want to achieve something in their lives. For these people we cannot talk about them such that they deliberately choose to eat everyday by free will, since they are not free to choose whether they are hungry or not. Same is also valid for most of the needs I just mentioned above that are already there when a subject is just a baby.
Now, some kind of free will comes into play when some of these (baby) needs suddenly are in conflict, in opposition with some other needs. To understand this, we have to admit that the more primitive needs can be overwritten, replaced by some more sophisticated needs. For example there are cases where people in the 9/11 disaster choose to "waste" some precious time in the towers to help other people to escape that inferno. Cases where the helpers were aware of the contradiction between their intuitive feeling to instantly leave the building due to high danger of death and their intuitive feeling that it is likewise or more valid trying to help others getting out.
The main aspect to consider here is what people judge to be worth doing or not doing (even worth thinking through or not thinking through!). So an element of judgement, a real element of belief in what worthiness things have or don't have comes into play. The terrorist may not have at all orchestrated their plans if they didn't thought that their goals are of a personal high worth. The same is true for all the helpers that died or have survived that day. In fact, such beliefs in a "higher" worthiness apart from the "primitive" needs of food, water and shelter can be observed on many occasions. As already mentioned there are suicides and hunger strikes in the world as well as wars to enforce "worthiness". But on the other side there are also kind acts of humanity all over the world that meet other definitions of "worthiness".
Since Osama Bin Laden was obviously very happy with the results of 9/11, it may have been the case that this satisfied his need for some "happiness" in his life. If true or not for that special person, most people obviously have very different beliefs of how to best satisfy their needs for happiness. And not only regarding their need for happiness, but also regarding their need for love, care and attention.
For me, the main point here is not the plethora of different "beliefs" in "worthiness" of different people that are often mutually conflicting each other. It is the fact that most human beings, during their lives, repeatedly come across two or more internally conflicting beliefs of "worthiness" already within their own hearts / souls / minds and have to make a decision. Whereas the more "primitive" needs like hunger are usually not conflicting with some other needs, belief-based needs can often do so.
Independent of what one thinks about the "worthiness" (or reliability concerning the truth of these beliefs) other people's various beliefs, these beliefs surely often lead to effective and irreversible results in physical reality. Moreover, weighing up two conflicting needs happens in the human mind and whether or not such a weighing up happens in a human's mind depends on another belief of that person, namely whether or not it is worth at all thinking more deeply about these two conflicting needs / beliefs / emotions.
Of course one can always "decide" that every decision the human mind makes is predetermined by the physics of the brain - even that very decision! That is another belief and, if true, the minds of all the people are populated with a plethora of beliefs that never can be proven / disproven constructively to be true or false - unless there would exist a method to explain how the brain can reliably differentiate true from false beliefs in all cases.
So we are left with a plethora of beliefs and don't even know whether or not they can be examined and analysed such that we are guaranteed to know whether or not there is any reality, any "worthiness" at their basis. We can't know that because we even cannot know what such a "basis" should look like, since a deterministic production of beliefs in the brain mustn't in any way coincide with the true ontology of ultimate reality, whatever it is. Nonetheless many scientist seem to believe that one day every truth about ultimate (physical) reality will be revealed to some human brains by means of deterministic processes in those brains such that these brains have complete knowledge about all that constituents of ultimate reality.
At this point it is a good guess that the plethora of conflicting beliefs in the world are all more or less trials to satisfy the variety of human needs enumerated above. It would be interesting to answer the question which of these beliefs is best suited for permanently satisfying these human needs. But as history, philosophy and a plethora of discussions at least since the age of enlightenment has shown, no overall consensus can be expected to arise for humanity concerning this question. Why? Because for analysing the whole issue, almost all steps of that analysis are themselves steps of belief in this or that.
So, if it is true that each and every human's life is driven by a set of more or less "primitive" internal needs / emotions, then every human is at first driven to satisfy its own internal primitive needs / emotions by its own internal "primitive" beliefs (for example "it is good to eat", "it is good to drink water", "it is good to have a shelter", "it is good to receive recognition" etc.). On the other hand, the resources to satisfy these needs may decrease from time to time - or steadily - via known and / or unknown causes.
We can surely state that there are many people who's needs are not served in this world. One now can react to this by ignoring these people or by at least being aware of them in one's own environment and trying to help them from time to time, even if some acts of little help require some acts of little sacrifice / relinquishment of one's own needs. Unless there would exist a method to explain how the brain can reliably differentiate true from false beliefs in all cases and therefore also figure out whether or not human decisions are indeed fully predetermined by the physics in the human brain, I would say that helping or not helping somebody, thinking or not thinking about one's own and others needs and how oneself handles these needs is in any case a personal decision that has indeed some kind of "free" will (in a binary sense) in it.