Before epilepsy was understood to be a neurological condition, people believed it was caused by the moon, or by phlegm in the brain. They condemned seizures as evidence of witchcraft or demonic possession, and killed or castrated sufferers to prevent them from passing tainted blood to a new generation.
What would evidence of free will look like?
I think the only reason there is “debate” is that free will is so intuitive and needed to justify institutions like the church and the current state of the justice system.
If you parse a lay description of free will, it’s clear from a 1980s biology perspective, that free will is an illusion. “I chose to pick up the pen” is how our brain rationalize our actions. A better sentence would be “My brain decided to pick up the pen and it made sense to do so in retrospect and I passively observed this process”.