Sabine Hossenfelder
Physicist and YouTuber; hard determinist, critic of beauty-driven physics, author of 'Existential Physics'
13 videos analysed · 29 quotes checked word for word · updated 2026-10-19
Key facts
- German, born in Frankfurt; PhD in physics from Goethe University Frankfurt (2003). Wikipédia · Sabine Hossenfelder (Wikipedia)
- Author of Lost in Math (2018) and Existential Physics (2022); her YouTube channel became her main activity by 2024. Wikipédia · Sabine Hossenfelder (Wikipedia)
Positions
click a row to see the evidenceA magazine interview calls her a self-proclaimed heathen and agnostic. In her book she lists the 'hypothesis of God' among the 'ascientific' ideas, those science cannot decide.
- She says science cannot justify conclusions about God, so she stays agnostic rather than claiming certainty either way. Article 2022 · Interview: Sabine Hossenfelder,…2
- She does not find a special purpose in the universe: the laws of nature seem to give rise to us by accident, and our universe is not even special in that regard. Video 2023 · What Could Be the Purpose of the…
The constants of nature are so finely tuned for life that this points to a designer.
She notes that other constants could also produce life, so our universe is not special for life.
Criticizes : The fine-tuning of the universe: too perfect a coincidence?
In Lost in Math she argues that physicists should be guided by experiments rather than by beauty, elegance or naturalness.
She assumes consciousness is a property that emerges in large collections of particles that are suitably connected and interacting. For all we know, she says, it is a property of systems that process lots of information. She rejects the idea that conscious attention changes what a wave-function collapses into.
- Her working assumption is that consciousness is a property that emerges in large collections of particles when they are suitably connected and interacting. Video 2024 · How could we tell whether AI has…
- She rejects the idea that conscious attention changes what a quantum measurement gives: such experiments were controversial and not reproduced. Video 2022 · Consciousness and Quantum…
- Since she takes consciousness to be a property of sufficiently complex systems that monitor and model themselves, she thinks some AI systems (not ChatGPT) may already be conscious to some degree. Video 2024 · How could we tell whether AI has…23
Conscious attention affects what a quantum measurement gives, so the mind is more than matter.
She says such claims of mind influencing quantum experiments are controversial and have not been reproduced.
Even a full physical account of the brain would leave out why there is something it is like to be conscious.
She says the future is fixed by the past, except for random quantum events that we cannot influence. She calls her position hard incompatibilism and says the idea of free will suggests "an inaccurate description of reality". In her words: "I think Free Will is incompatible with determinism. I also think it's incompatible with indeterminism." Since the real world mixes both, free will does not exist. She has no quarrel with compatibilism, which she sees as a matter of definition.
- Free will would need a choice that is neither fixed by the past nor random. She says the laws of nature are either deterministic or random, so it is incoherent in both cases. Video 2023 · I don't believe in free will.…2
- Quantum randomness does not rescue it: those random events are not influenced by anything, so not by your will either. Video 2021 · Does Superdeterminism save…2
- If free will were something non-physical, it would explain nothing in the physical world, so she sees no reason to invent it. Video 2023 · I don't believe in free will.…
- She does not object to compatibilists who simply redefine free will, but for her that is only a matter of definition. Decisions still matter, predetermined or not. Video 2023 · I don't believe in free will.…2
Free will can be defined so that it fits with determinism (compatibilism).
She does not object to compatibilism, which she sees as a matter of definition, and holds that free will in the ordinary sense is incompatible with both determinism and indeterminism.
If the future is already fixed, our decisions do not matter.
She says decisions matter even if the future already exists and is predetermined.
See 1 more objections
Free will can be non-physical: a soul or will that acts on the body from outside.
She dismisses non-physical free will as explaining nothing about the physical world.
Defends : The intellect that would see the whole futureMixed : Liberty is opposed to constraint, not to necessityCriticizes : The infinite will: what makes us like God
She says each person must answer the question of meaning for themselves. She cites her mother's view that the meaning of life is to pass knowledge to the next generation. She also says the laws of nature do not care about us; they gave rise to us by accident, and it is a bit self-centred to think the universe's only acceptable point would be to create life.
- She says science has not revealed a point to the universe in the sense of purpose or intention: the laws of nature do not care about us and give rise to us by way of an accident. Video 2023 · What Could Be the Purpose of the…
- She finds it self-centred to say the only acceptable point of the universe would be to create life. Video 2023 · What Could Be the Purpose of the…
A universe without any purpose for life would be pointless: its point must be to produce life.
She finds it self-centred to say the only acceptable purpose of the universe is to create life; the laws of nature do not care about us and gave rise to us by accident.
No sourced position yet on: Certainty, Status of morality, Faith and reason, Human nature.
On the big questions
Does God exist?Agnosticism
Self-described agnostic; she says science cannot justify conclusions about God.
- She says science cannot justify conclusions about God, so she stays agnostic rather than claiming certainty either way. Article 2022 · Interview: Sabine Hossenfelder,…2
- She does not find a special purpose in the universe: the laws of nature seem to give rise to us by accident, and our universe is not even special in that regard. Video 2023 · What Could Be the Purpose of the…
The constants of nature are so finely tuned for life that this points to a designer.
She notes that other constants could also produce life, so our universe is not special for life.
Criticizes : The fine-tuning of the universe: too perfect a coincidence?
The question on the site: all the argumentsDoes life have a meaning?A meaning to create
Meaning is a personal answer, not a given.
- She says science has not revealed a point to the universe in the sense of purpose or intention: the laws of nature do not care about us and give rise to us by way of an accident. Video 2023 · What Could Be the Purpose of the…
- She finds it self-centred to say the only acceptable point of the universe would be to create life. Video 2023 · What Could Be the Purpose of the…
A universe without any purpose for life would be pointless: its point must be to produce life.
She finds it self-centred to say the only acceptable purpose of the universe is to create life; the laws of nature do not care about us and gave rise to us by accident.
Are we free?No free will
Her 2020 video title says it: 'You don't have free will, but don't worry'.
- Free will would need a choice that is neither fixed by the past nor random. She says the laws of nature are either deterministic or random, so it is incoherent in both cases. Video 2023 · I don't believe in free will.…2
- Quantum randomness does not rescue it: those random events are not influenced by anything, so not by your will either. Video 2021 · Does Superdeterminism save…2
- If free will were something non-physical, it would explain nothing in the physical world, so she sees no reason to invent it. Video 2023 · I don't believe in free will.…
- She does not object to compatibilists who simply redefine free will, but for her that is only a matter of definition. Decisions still matter, predetermined or not. Video 2023 · I don't believe in free will.…2
Free will can be defined so that it fits with determinism (compatibilism).
She does not object to compatibilism, which she sees as a matter of definition, and holds that free will in the ordinary sense is incompatible with both determinism and indeterminism.
If the future is already fixed, our decisions do not matter.
She says decisions matter even if the future already exists and is predetermined.
See 1 more objections
Free will can be non-physical: a soul or will that acts on the body from outside.
She dismisses non-physical free will as explaining nothing about the physical world.
Defends : The intellect that would see the whole futureMixed : Liberty is opposed to constraint, not to necessityCriticizes : The infinite will: what makes us like God
The question on the site: all the argumentsIs the mind the brain?The mind comes from matter
Consciousness emerges from suitably connected particles; she thinks some AI systems may already be conscious to some degree.
- Her working assumption is that consciousness is a property that emerges in large collections of particles when they are suitably connected and interacting. Video 2024 · How could we tell whether AI has…
- She rejects the idea that conscious attention changes what a quantum measurement gives: such experiments were controversial and not reproduced. Video 2022 · Consciousness and Quantum…
- Since she takes consciousness to be a property of sufficiently complex systems that monitor and model themselves, she thinks some AI systems (not ChatGPT) may already be conscious to some degree. Video 2024 · How could we tell whether AI has…23
Conscious attention affects what a quantum measurement gives, so the mind is more than matter.
She says such claims of mind influencing quantum experiments are controversial and have not been reproduced.
Even a full physical account of the brain would leave out why there is something it is like to be conscious.
Is the world real?The world is real
She rejects the simulation hypothesis as pseudoscience.
- The simulation hypothesis is not a scientific argument, and she says it mixes science with religion, which is generally a bad idea. Video 2021 · The Simulation Hypothesis is…
It is likely that we live in a simulation, because simulated minds would far outnumber real ones.
She says the simulation hypothesis is not a scientific argument and mixes science with religion.
Criticizes : The simulation argument: three possibilities, one of which is true
The question on the site: all the argumentsCan science explain everything?True, but not everything
She says science will probably never answer all the big questions; she writes that where it ends, 'we seek other modes of explanation'. She says she is not 'a cheerleader for science': some of it is great and some is not.
- She says we do not know how our universe began and may never know, so science will probably not answer every big question. Article 2023 · Sermon illustration quoting…2
- She wants science kept strict: a model should only be made more complicated if data or an internal inconsistency requires it, otherwise it is not a scientific hypothesis. She calls worries such as the absence of unification or small parameters aesthetic misgivings, not real problems. Video 2023 · What's Going Wrong in Particle…2
- She says she is not a cheerleader for science: some of it is excellent and some is not, and the crisis in physics is real. Video 2024 · The crisis in physics is real:…2
Open problems like unification or small constants in physics are real puzzles that need new theories.
She says most of these claimed problems are only aesthetic worries, and that a model should be made more complicated only if data or internal inconsistency requires it.
Defends : A theory is scientific if it can be refuted
The question on the site: all the argumentsDoes time really exist?Passage is an illusion
She believes the block universe is how nature really works: the special status of the present is a false perception.
- Physics, she says, has no special present moment; our feeling that the present is special is just wrong. Video 2026 · This is why I believe that the…
We know only our present experience: the present moment is special, not one slice among others.
Defends : There is no 'now' for the whole universe: past, present and future form a block
The question on the site: all the argumentsIn their words
The future is fixed by the past, except for random quantum events that we cannot influence.
Where science ends, we seek other modes of explanation.
Free Will is logically incoherent nonsense
I think Free Will is incompatible with determinism I also think it's incompatible with indeterminism
1 more quotes
It matters a lot what decisions you make, whether those were predetermined or not.
How the ideas evolved
Click a step for details2012A scientific meaning for 'free will'
In a paper called 'The Free Will Function', she argues that free will and the act of choosing can be given an operational, scientific meaning without metaphysics.
2018Lost in Math
Her first book argues that theorists rely too much on beauty, elegance and naturalness, and that this has led physics astray. She asks why the laws of nature should care what we find beautiful.
2020'You don't have free will, but don't worry'
In this video she argues that the whole story of the universe was determined at the Big Bang, apart from random quantum events we do not influence. She adds that the thinking you do is itself determined, but you still have to do it. With Tim Palmer she also publishes a paper on superdeterminism.
2021Superdeterminism and the 'pseudoscience' of simulation
She says it is obvious to her that superdeterminism is the right explanation of quantum observations, and that Einstein was right about quantum mechanics. The same year she argues that the simulation hypothesis is not a scientific argument and mixes science with religion.
In their words« i don't think popularizing the simulation hypothesis is entirely innocent fun it's mixing signs with religion which is generally a bad idea »She criticizes the simulation hypothesis as mixing science with religion. watch
« before i explain why the simulation hypothesis is not a scientific argument »She says the simulation hypothesis is not a scientific argument. watch
« for all we currently know consciousness is simply a property of certain systems that process large amounts of information »She treats consciousness as a property of systems that process information, whatever their physical basis. watch
2022Existential Physics
Her second book asks what physics says about the big questions: God, free will, consciousness, other universes, simulations. She sorts some of them as 'ascientific', beyond what science can test.
2023'Hard determinist'
A blog post on one of her videos reports that she declares herself a hard determinist and says we lack libertarian free will in the commonly accepted sense.
2023Free will fails under both determinism and indeterminism
In a video on why she does not believe in free will, she holds it is incompatible with determinism and with indeterminism. If free will is not physical, she says, it explains nothing about the physical world. In the same year she argues that most 'problems' in particle physics are only aesthetic worries.
In their words« they are just aesthetic misgivings in fact if you look at the list of unsolved problems in the foundations of physics »She says most claimed problems in foundational physics (unification, small parameters) are only aesthetic worries. watch
« the problem is that those models with all their different predictions are unnecessarily complicated they should never have been put forward they are not scientific hypotheses »She criticizes models that complicate the standard model without data requiring it: not scientific hypotheses. watch
« there are only two justifications for making a model more complicated the first is if you already have data that requires it »She says a model should be made more complicated only if data or internal inconsistency requires it. watch
2023What could be the purpose of the universe?
She says the laws of nature do not care about us and gave rise to us by accident. Other constants could also produce life, so our universe is not special in that respect.
In their words« it seems that the laws of nature don’t care about us, or anything like us, it’s rather that they give rise to us by way of an accident »She says the laws of nature do not care about us and gave rise to us by accident. watch
« So our universe isn’t even special in this regard. »She notes other constants could also produce life, so our universe is not special for life. watch
« to me this interpretation of “point” seems to say that the only acceptable “point” of the universe would have been to create life. I think that’s a bit self-centred »She finds it self-centred to think the only acceptable purpose of the universe is to create life. watch
2024Consciousness in AI
She assumes consciousness emerges in large collections of suitably connected particles, and says some AI systems (not ChatGPT) are already conscious to some degree.
In their words« first assumption I'll make about Consciousness is that it's some property which emerges in large collections of particles if these particles are suitably connected and interacting »She assumes consciousness emerges in large, suitably connected collections of particles. watch
« why I think that other AI systems are conscious already why they'll become more conscious rapidly »She says some AI systems (not ChatGPT) are already conscious to some degree. watch
2026 Change of mindThe future already exists
She says the block universe is how nature really works and a special present is an illusion. She used to think the past becomes fixed only after a measurement and has changed her mind. She adds that decisions still matter, predetermined or not.
In their words« This is why I think the block universe is how nature really works and that our perception of the present moment being somehow special is just false »She thinks the block universe is how nature works and that a special present moment is false. watch
« Now I used to think that this means it's only after you've made a measurement that the past becomes fixed »She says she used to think the past becomes fixed only after a measurement, and has since changed her view. watch
« It matters a lot what decisions you make, whether those were predetermined or not. »She says decisions matter even if the future already exists and is predetermined. watch
The arguments 7
The site's arguments they defend or criticize, and why. Click a title to see the full argument.
She says quantum indeterminism does not rescue free will: random processes are not influenced by anything, so they are not influenced by your free will either.
She has no problem with compatibilism: define free will as you like, it is just a definition. She still concludes that free will, in the usual sense, does not exist.
She says a model should be made more complicated only if data requires it. Models piled on the standard model without such data 'are not scientific hypotheses'.
She thinks the block universe is how nature really works: a special present moment is just a false perception.
She calls the simulation hypothesis pseudoscience: it makes a bold claim about the laws of nature without paying attention to what physics already knows. In her words, popularizing it is not innocent fun: it mixes science with religion, 'which is generally a bad idea'.
She dismisses a non-physical free will: it explains nothing in the physical world, so why invent it.
She notes that other values of the constants could also produce life, so our universe is not even special in that regard.
Allies and opponents
Albert EinsteinClose
She agrees with Einstein that quantum mechanics is deterministic rather than inherently random. She says: 'I think Einstein was right about quantum mechanics.'
William Lane CraigDisagrees
They were on the same debate panel on God. She questioned whether science can justify conclusions like those Craig draws from the universe's beginning and fine-tuning.
Signature ideas
Superdeterminism
She holds that quantum mechanics only looks random: measurement outcomes are fixed by hidden variables, which depend on what will be measured. She says this could be tested, as outcomes might turn out to be more predictable than standard quantum theory allows.
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All sources (33)
- Sabine Hossenfelder (Wikipedia) Wikipedia
- More on free will from Sabine Hossenfelder Why Evolution Is True (Jerry Coyne) · 2023
- Does quantum mechanics rule out free will? Scientific American (John Horgan) · 2022
- Sabine Hossenfelder says we don't have free will, but its nonexistence shouldn't bother us (video 'You don't have free will, but don't worry') Why Evolution Is True (Jerry Coyne) · 2020
- Interview: Sabine Hossenfelder, author of Existential Physics Hippocampus Magazine · 2022
- The trouble with beauty (review of Lost in Math) Physics World · 2018
- The Free Will Function (arXiv 1202.0720) arXiv · 2012
- The Battle for Reality: Does God Exist? Craig, Williams, Hossenfelder and Žižek Premier Unbelievable? · 2026
- Sermon illustration quoting Existential Physics (p. 218) Christianity Today (Preaching Today) · 2023
- Review of Sabine Hossenfelder's Existential Physics (John G. Messerly) Goodreads (author blog) · 2023
- Sabine Hossenfelder on free will and 'superdeterminism' of quantum mechanics Why Evolution Is True (Jerry Coyne) · 2021
- Why the simulation hypothesis is pseudoscience Big Think (read from search summary) · 2021 *
- Sabine Hossenfelder's video "The Simulation Hypothesis is Pseudoscience" Substack (critical review of her video) · 2021 *
- The Simulation Hypothesis is Pseudoscience YouTube (Sabine Hossenfelder) · 2021
- Does Superdeterminism save Quantum Mechanics? Or does it kill free will and destroy science? YouTube (Sabine Hossenfelder) · 2021
- What's Going Wrong in Particle Physics? (This is why I lost faith in science.) YouTube (Sabine Hossenfelder) · 2023
- I don't believe in free will. This is why. YouTube (Sabine Hossenfelder) · 2023
- How could we tell whether AI has become conscious? YouTube (Sabine Hossenfelder) · 2024
- The crisis in physics is real: Science is failing YouTube (Sabine Hossenfelder) · 2024
- I don't believe in free will. This is why. YouTube (Sabine Hossenfelder) · 2023
- Does Superdeterminism save Quantum Mechanics? Or does it kill free will and destroy science? YouTube (Sabine Hossenfelder) · 2021
- What Could Be the Purpose of the Universe? YouTube (Sabine Hossenfelder) · 2023
- The Simulation Hypothesis is Pseudoscience YouTube (Sabine Hossenfelder) · 2021
- Consciousness and Quantum Mechanics: How are they related? YouTube (Sabine Hossenfelder) · 2022
- I don't believe in free will. This is why. YouTube (Sabine Hossenfelder) · 2023
- This is why I believe that the future already exists YouTube (Sabine Hossenfelder) · 2026
- The crisis in physics is real: Science is failing YouTube (Sabine Hossenfelder) · 2024
- What's Going Wrong in Particle Physics? (This is why I lost faith in science.) YouTube (Sabine Hossenfelder) · 2023
- How could we tell whether AI has become conscious? YouTube (Sabine Hossenfelder) · 2024
- This is why I believe that the future already exists YouTube (Sabine Hossenfelder) · 2026
- Does Superdeterminism save Quantum Mechanics? Or does it kill free will and destroy science? YouTube (Sabine Hossenfelder) · 2021
- The Simulation Hypothesis is Pseudoscience YouTube (Sabine Hossenfelder) · 2021
- This is why I believe that the future already exists YouTube (Sabine Hossenfelder) · 2026