Understanding how the brain functions has a huge impact, for instance in the field of mental health. Harris being a neuroscientist is in the field learning to understand how the brain functions. While
anyone can philosophize, including Harris, this
particular book of his I chose to recommend in this conversation
because he's speaking as a scientist. I understand why it might be uncomfortable to think that free will may only exist to a limited degree, or not at all, and I found this work of Harris' on the subject intriguing because it brings up
extremely uncomfortable questions (as I recall, none of which are religious in nature). I personally think Harris' often gets dismissed out of hand by some because of his outpokenness on the subject of religion, and while he does write a lot about religion, he's not a one-trick-pony.