Sentence:  The new challenge to <WSD>free will</WSD> comes from a different direction: neuroscience's discovery that people's brains are a collection of diversely oriented modules, and that our understanding of our own intentionality is to a great degree a legitimating fiction which one module in the left hemisphere of the brain retroactively imposes over the decisions different modules make. 
Meaning of the word marked with <WSD> tags:  The ability to choose one's actions, or determine what reasons are acceptable motivation for actions, without predestination, fate etc.