This is an interesting read.
“Our attitude to the free will question is intimately linked to the dualism-monism debate. Dualists believe that there are two separate entities, soul (or mind) and brain, and most maintain that they somehow interact, following Descartes. Monists deny a separate soul, saying that everything is matter. This links in with the question of free will, because if you believe in a separate nonphysical soul/mind that somehow influences the brain, you must assume that conventional physical and chemical forces do not completely determine brain function.”
I’m monist, but I don’t see how dualism would allow for free will either since you still can’t escape the causal/acausal dichotomy. It’s not like your could have created your brain or soul before you existed to have the brain or soul.