If causation dictates all, then free will cannot exist. Your neurons are wired a certain way; your synapses follow neural pathways that form your mental architecture, a predictable result of genetics and random life experiences within circumstantial environments. Everything you perceive, analyse and conclude must go through your mental processes. Your whole sense of reality relies not on objective senses but on your unique individual neural network.
To have will means to be bound by your brain’s parameters. To will is to serve your self-framework. You are a mouse free to roam in his maze.
Free will cannot exist… Perhaps this realisation is the only measure of free will we can attain - and maybe that’s good enough.
The freest slave is he who understands he is a slave. Slaves with delusions of freedom are forever bound by servitude and blissful ignorance.
This is not a deterministic message, nor is it one of denial of agency or accountability. Far from it. If anything, the delusion of free will is what denies self-accountability by driving you to claim false credit for things you did not objectively earn or deserve. How self-accountable can you then be?