Action, Knowledge, and Will

What is the difference between the movements in our bodies we cause personally ourselves, such as the movements of our legs or our lips when we walk or speak, and the movements we do not cause personally, such as the contraction of the heart? Is an act that is done under duress done voluntarily, out of choice? Should duress exculpate a defendant completely, or should it merely mitigate the criminality of an act? When we explain an intentional act by stating our reasons for doing it, do we e...