These laws have the common property that if you have an initial condition at one moment in time, for example the exact details of the particles in your brain and all your brain’s inputs, then you can calculate what happens at any other moment in time from those initial conditions. This means in a nutshell that the whole story of the universe in every single detail was determined already at the big bang. We are just watching it play out.I think there are at least three problems with her argument.
First, she's basing her conclusion that free will is an illusion on an unprovable metaphysical assumption, the assumption that materialism is true. If it is true then determinism does seem to be the most reasonable position. If, as she claims, all we are is particles of matter then it's not hard to believe that - like planets, stars and every other material object in the universe - we're totally in thrall to physical laws.
However, there's no compelling reason to accept her assumption that materialism is true. She holds it simply as a metaphysical or psychological preference, and if materialism is false, if human beings possess immaterial minds not subject to physical determinism and which work somehow in concert with the material brain, then our overwhelming conviction that we have freedom of choice may not be an illusion at all.
In fact, the conviction of freedom is one reason for thinking that there actually is more to us than just our material selves. In any case, in lieu of a compelling reason to think materialism is true, her argument for determinism is unconvincing.
The second problem is that if materialism is true then our beliefs are merely the epiphenomena of particles whizzing around in our brains, and there's no reason to think that truth, especially truth about metaphysical matters, can emerge from mindless particles banging against each other.
Thus, given her belief in materialism, Hossenfelder has no good reason to think that her metaphysical beliefs are true, including her belief in materialism.
Moreover, if everything is determined then our beliefs are determined, and it follows that Hossenfelder's belief in materialism is a product of influences, many of them unconscious, that have acted on her throughout her life.
Given those influences it was inevitable that she'd be a materialist, but if her belief in materialism is largely the product of the unconscious effects of childhood experiences why should we be expected to accept an argument that reduces to something like "given my childhood experiences I [Hossenfelder] am convinced that materialism/determinism are true"?
Likewise, if materialism and determinism really are true but her listeners nevertheless reject them, they're not being irrational because their rejection is a decision that they were predetermined ever since the Big Bang to make. They could not have done otherwise. No decision we make in life could have been other than what it is.
There's no scientific argument that can demonstrate that materialism is true and good reasons to think it's not, but many scientists like Hossenfelder take it as their starting assumption because they find it psychologically congenial. Her entire argument for determinism, however, is predicated upon that assumption. It's the reason she privileges her faith in the laws of physics over the powerful experiential intuition that we're somehow free, and it's the reason she concludes that the powerful intuition of freedom must be an illusion.
Here's a third problem with her presentation.
In the video (8:05) she mentions moral behavior, but she's careful not to talk about it in terms of right and wrong acts. She's correct to avoid this language because if materialism/determinism are true there can be no moral right or wrong. People do what they're determined to do and though there may be a kind of responsibility in the sense which she explains it, there's no moral responsibility and no moral guilt.
If my behavior harms others they may not like it, and if they have the power to punish me they will, but that doesn't mean that I've done anything for which I should feel guilt or remorse. Humans, if we are determined, should no more feel remorse for harming others than a shark feels remorse for attacking a surfer.
The fact that we know what we're doing when we harm another and the shark doesn't know makes no practical difference. If we were programmed, as it were, to harm others and couldn't have done otherwise, then our awareness of what we're doing is irrelevant. There's no moral guilt, and feelings of guilt and remorse are merely a psychological trick played on us by nature.
Our belief that we are in some sense free, if we have that belief, is a properly basic belief. We're rational to hold it - given the powerful intuition we have that we really are free - unless and until we're faced with a compelling defeater for that belief. Hossenfelder's presentation is only compelling if one accepts her materialism, but why think materialism is true?
She doesn't tell us.