physicists have a long history of sticking our noses where they don't belong and one of our favorite places to step beyond our expertise is the question of consciousness and free will sometimes our musings are insightful sometimes incoherent and usually at least somewhat naive which is a fair description of this show so of course space-time needs to weigh in on the subject of physics and free will in recent episodes we explored the notion of determinism in the context of the block universe idea that we get from einstein's relativity in it the past and future have a sort of eternal timeless existence from the point of view of some god-like observer outside both space and time and this naturally brings into focus the question of how physics relates to the concept of free will the most evocative expression of perfect determinism is given by laplace's demon in 1814 pierre simon laplace postulated that a sufficiently vast intellect that had perfect knowledge of the current state of the universe like the positions and velocities of all particles and perfect knowledge of the laws of nature could calculate perfectly all future states of the universe if you accept that the mind is generated by the brain which is made of matter and you've already accepted that matter follows the cold inviolable laws of nature then your mind every single thought choice decision is the inevitable result of the long chain of cause and effect that came before it and what you do next also is already determined laplace's demon knows whether or not you'll decide you believe in free will there are many ways of looking at the concept and question of free will we are not going to pretend to give any definitive answers regarding its reality but we do want to look at the most popular way this question is positioned in physics the idea that determinism negates free will is it really that simple one note before i go further yes we'll mention the quantum but importantly that is not to say that free will or consciousness are necessarily related to it we'll talk about that connection or lack thereof another time but understanding the implications of quantum mechanics is key to unraveling determinism and its connection to predictability quantum mechanics seems to tell us that one of the following is true either the outcomes of quantum scale events are fundamentally random or the outcomes of quantum events are perfectly determined by quantum laws and the apparent randomness comes from our limited perspective let's unpack these possibilities and what they imply for free will by looking at it in terms of information one of the most important rules of quantum mechanics is the principle of conservation of quantum information it just says the quantum information can never be destroyed or created out of nothing we've talked about why this is such a fundamental law previously let's paint a cartoon representation of quantum information in a block universe two dimensions of space in one of time the slices of the block universe represent the causal ordering of the universe lower layers cause layers above them each bit of quantum information can be represented as a thread threads are evolving quantum states these may transform and become entangled with each other but if quantum information is conserved a thread can never vanish nor start out of nothing we'll ignore what happens at the beginning of time for today tangled networks of these threads may spend time as different types of matter and sometimes as brains both as the crude matter that forms the brain and the ephemeral configuration of neural connections synaptic strengths and electrochemical dynamics from which we think emerges our experience of our minds so information goes in as the stuff of the brain and the experience of our senses and information comes out sometimes in the form of the choices we make the brain is like a machine for processing information into choices we can parcel that decision-making machine off from the rest of the universe and we can ask what has to happen inside this patch for us to reasonably attribute free will to it there are different ways we could define free will in this picture we could require that information emerging from the brain in the form of a decision either one incorporates an entirely new thread of quantum information in violation with the conservation principle or two that this information just not be predictable even in principle by any arbitrarily precise far future brain scanning technology and there are other requirements we could place like three that the future not be predefined and not singular or four we could require that the choice not depend on any underlying non-free willed mechanistic process whether that process is deterministic or random i'm going to argue that it's reasonable to endow the brain with free will with some combination of the first three if we demand number four that there's no underlying non-free-willed mechanics to the process of choice then free will probably is indeed dead but i'll also argue that this is an unreasonable ask let's start with one and two you are free-willed if new or fundamentally unpredictable information can emerge from your brain's patch of space-time now creating brand new information explicitly violates conservation of quantum information that said the most mainstream interpretation of quantum mechanics has the same problem the copenhagen interpretation insists that the apparent randomness of quantum events is really random the quantum information in the state of the wave function before collapse is destroyed but information is also created the outcome of quantum interactions are chosen in fundamentally unpredictable ways information threads both end and begin at every wavefunction collapse the idea of random processes driving our choices doesn't really sound like free will so is there any possible way to generate new information that isn't random that's somehow intentional well actually not really think about a new thread of quantum information starting from nothing let's say emerging from a packet of space time where no information enters by definition it has no cause but the notion of choice implies a deliberate cause to that bit of information being intentionally say a one or a zero rather than randomly a one or a zero but that cause is by definition a thread of in-going information if the cause arises within our packet within our brain then either it itself is random or has its own causing thread whose origin is either in our brain and uncaused random or has an origin outside our brain meaning our brain didn't choose you could say that the cause arises outside the universe in a supernatural sense but then all we need to do is expand our definition of the universe to all things causally connected and we reach the same conclusion the only way for new information to come from a closed region is for it to be generated randomly within that region on the surface the idea of randomly generating new streams of quantum information within a brain doesn't seem to help the cause of free will i'll argue shortly that there's a notion of free will in which it doesn't matter the origin of the unpredictability of choice but let's first look at another source of that unpredictability even in a deterministic universe laplace's demon is a fiction it's not just impossible in practice to perfectly measure all the states of a brain of neurons their activity the molecules involved in their signaling etc it's also impossible in principle by that i mean there's a fundamental limit to the amount of information that can be collected about a system forget the brain that's true even for a box full of air molecules this is a direct consequence of the heisenberg uncertainty principle which tells us that measuring one property perfectly leaves a counterpart property perfectly undefined so there is no possibility to perfectly know the state of the brain or of the information threads that go into making it either in principle or in practice because unknown random processes are at work and or perfect measurement is not possible for any entity that could possibly exist but is the impossibility of perfect predictability enough to endow us with free will what if some future type of brain scan allows 98 predictability of your choices this is actually a very interesting area of research which we may talk about another time but the short story is that even for the simplest decision the best people have done is to predict just a bit above chance at 60 to 70 percent accuracy and retrospectively which means you could ask if it's even prediction or really just finding a correlation between a brain state and an outcome a few seconds later and don't quote the famous labet experiment at me it's been thoroughly cast in a new light the short answer is we don't know how well we'll ever be able to forward model a brain's behavior even with the best future technology by the way there's also evidence to indicate that brain activity utilizes the random fluctuations of neuronal activity to make certain decisions in other words a certain type of randomness may be a feature of the brain an item in its mechanistic toolbox so even the all-knowing laplace demon may be out of luck especially if quantum randomness or quantum indeterminacy is magnified to brain level activity again not saying consciousness is quantum we'll talk more about that soon another important consideration is whether or not the future is actually singular and determined regardless of the existence of any agents of choice in the copenhagen interpretation the future is singular but undetermined one future will happen but it's impossible to predict what it will be in the many worlds interpretation the future is plural and determined all possible futures exist and develop according to the laws of quantum mechanics in either case there's a place for a fair notion of free will either our brains play a part choosing what future happens or the choices we experience are the process of choosing which many worlds future we travel towards even if other versions of us choose otherwise the case where free will may really struggle is the case of a singular determined future you can get this sort of singular hard determinism with things like de broglie bone pilot wave theory but fortunately for free will such interpretations don't look like they're correct at least as they currently stand let's talk about the fourth argument against free will in my earlier list that a purely mechanistic process can't lead to any reasonable notion of free will so we've established that there are plausible ways in which fundamental unpredictable information perhaps in the form of choices can emerge from a brain so this nexus of quantum information processing may truly be an unpredictable black box decision making machine at least some of the time add to that the fact that its emergent phenomenon conscious free will can recursively influence the machine itself the brain can talk itself into new states could that be enough to designate it free willed some would argue no if there's a mechanistic substrate to generating this phenomenon which is founded in either deterministic or random processes then the phenomenon is an illusion but i think it's a reductionist fallacy to deny an emergent phenomenon any properties not also possessed by its parts a red apple is made of atoms but atoms possess neither redness nor appleness yet we don't say that apples are an illusion if it's not even in principle possible to perfectly predict a brain's choices and that brain feels like it's making choices is it reasonable to deny meaningfulness to the concept of free will just because the brain's atoms don't have free will the same goes with your conscious experience it's not an illusion it's an emergent phenomenon and it's the most directly verifiably real thing you will ever observe you don't choose the mechanical behavior of your brain's atoms or the electrical potential that triggers each firing neuron those things are the substrate of your choices and your choices are you in the end this is all semantic there are definitions of free will that we probably don't have but both physics and neuroscience tell us that we can probably call ourselves free willed by a number of very reasonable and functional definitions ultimately many agree that the question is just badly posed when you ask is free will an illusion what do you mean by free or will or illusion or is for that matter well you go ahead and enjoy the very convincing illusion that you are going to go down a recursive rabbit hole deciding whether you have the free will to decide if free will exists i'm now going to exercise my free will to not end this episode with me saying space time [Music] you