On two levels we have no free will -
First. Inherently, if you rewound the universe, didn't change anything, I would still be typing this sentence. Thats the easiest one.
But more practically and tied to observation - (I am putting the following in quotes as I got it summarised for me, the take away is that actions are set significantly before we think we make a choice)
"A bunch of “free choice” lab studies suggest that what you experience as a conscious decision is often a late step in a longer chain of brain processes. In classic decoding work, patterns of activity in frontal and parietal regions carry information about which option someone will pick several seconds before they report being aware of deciding, implying the choice is already being shaped before conscious intention shows up.
EEG studies of voluntary movement show a readiness potential (a slow build-up before action). More recent interpretations model this as noisy brain activity accumulating toward a threshold, which makes “the brain ramps up, then you move” less like a single moment of conscious initiation and more like an unfolding preconscious process. A neat twist is BCI work showing people can sometimes still veto an about-to-happen movement, but only up to a short “point of no return” close to movement onset, suggesting conscious control may be limited to a late, narrow window. "
Soon et al. (2008) - Unconscious determinants of free decisions in the human brain (Nature Neuroscience)
https://www.nature.com/articles/nn.2112
Schurger et al. (2012) - An accumulator model for spontaneous neural activity prior to self-initiated movement (PNAS)
https://www.pnas.org/doi/10.1073/pnas.1210467109
Schultze-Kraft et al. (2016) - The point of no return in vetoing self-initiated movements (PNAS)
https://www.pnas.org/doi/10.1073/pnas.1513569112
Maoz et al. (2019) - Neural precursors of decisions that matter (eLife)
https://elifesciences.org/articles/39787
I also think we live in a block time universe which constantly tickles me.