Neurophysiologist Benjamin Libet has demonstrated in experiments that every conscious decision to act is preceded by brain activities that have already determined the action. What follows from this? Brain researchers like Gerhard Roth and Wolf Singer claim: Our will is not free; our actions are determined. If this claim is true, it has serious consequences: everything from criminal law to our self-understanding as humans would be up for debate. But is the subjective impression of acting freely really just an illusion? Are the laboratory findings self-explanatory? Who decides on their interpretation? Natural scientists or social scientists? This complex of questions was addressed in a series by the Frankfurter Allgemeine Zeitung, the contributions of which are presented here in an expanded and revised form along with other texts on the topic.