“Pleasure to me is wonder—the unexplored, the unexpected, the thing that is hidden and the changeless thing that lurks behind superficial mutability. To trace the remote in the immediate; the eternal in the ephemeral; the past in the present; the infinite in the finite; these are to me the springs of delight and beauty.” ~ H.P. Lovecraft
The brain is not a single-purpose organ, so the idea that its decisions are determined only by chemestry/genes cannot be accurate. Because it has an open-ended functionality, and is responsive to the environment, and most importantly, possesses consciousness, there cannot be a direct line between physical forces and decision making.