BBC botches physics in series on free will

The BBC recently came out with a three-part series on free will. Part 2 is about physics. If you’re going to infer lessons from physics, it helps to get the physics right. They don’t. Part 2 of the BBC series can be found here:

The picture above analogizes a series of physical events to a chain of dominoes, in order to talk about cause and effect. But there’s something odd about this metaphor, if the dominoes are supposed to represent the physical universe: look at that first domino, in black. What makes it tip over? Something from outside the universe, a “god” so to speak, intervenes to set the whole thing in motion. We seem to have jumped from physics to theology.

This would just be a nit-pick, if the negligent treatment of the “start” in the model did not affect the conclusions drawn. But it does, as we will see.

But first let’s look at some additional physics mistakes in the video. Jim Al-Khalili says “When we think we’re making free choices, it’s just the laws of physics playing themselves out.” Well no, the laws of physics alone don’t cause anything. The laws of physics are rather abstract. If you want to understand how a concrete action came about, you need not just laws of physics but also what physicists call “boundary conditions”, AKA concrete reality. Especially bits of concrete reality that heavily interact with the action in question. For example, you. Of course, perhaps Al-Khalili didn’t mean “just the laws of physics” quite so literally. But it matters how you phrase things, especially when you accuse people of only thinking they’re making free choices. Your grounds for calling them mistaken had better not be based on distorted depictions of the physics.

From the “libertarian” side of the philosophical debate, Peter Tse makes a different mistake – or maybe just poorly worded statement: “Patterns of energy don’t obey the traditional laws of physics.” Unless he means “classical physics” (in which case: say “classical”), that’s not true. The Wikipedia article on Lagrangian mechanics is a good resource for seeing just how deeply physics treats patterns of energy. “The kinetic and potential energies still change as the system evolves, but the motion of the system will be such that their sum, the total energy, is constant.”

Block universe as a loaf of bread, from BBC video

Since Einstein, physicists have known that space and time are not independent, but aspects of a single four-dimensional manifold, spacetime. For observers in different inertial reference frames, which direction counts as “time” will differ. A metaphor called the “block universe” is sometimes used to describe this, where we only depict two spatial dimensions and then repurpose the third to represent time. Jim Al-Khalili uses a loaf of bread, with different times being different slices.

The block universe is like a loaf. OK, let’s go with this metaphor: one end of the loaf is very hot (we call it the Big Bang) and the other is cold. There are certain patterns that stretch from one end of the loaf to the other. If we know the pattern (laws of physics) and we know the boundary conditions (full state of any slice) we can derive the state of any other slice. Why say that the hot end caused the cold end to be the way it is? Why not say that the cold end caused the state of the hot end? After all, the mathematical derivation works equally well in that direction. Better yet, why not admit that “causality” is a useless concept at the level of a complete description of the universe, and just look at the bidirectional laws of nature instead? Why not start your analysis in the middle (but nearer to the hot side), and work your way toward both ends? The last option is a lot more practical, since that middling point is where you are.

The idea that the Big Bang is the Big Boss and we are just its slaves has no basis in science. Remember that “god” that tipped over the first domino? He’s creeping back in through the back door of Al-Khalili’s thinking. He thinks the Block Universe is dominated by its early times. You can only get such domination by swapping out a scientific view of time and causality, and sneaking in an intuitive picture of time and causality in its place.

Al-Khalili does that when he says “The past hasn’t gone … the future isn’t yet to be decided.” The narrator does that when she says “every single frame of that animation already exists and will exist forever.” Argh, no! Time is within the loaf! If you’re going to use a metaphor, stick with the structure you used to create it – don’t sneak your intuitive conception of time into the background while leaving scientific time in the foreground, now portrayed spatially.

Al-Khalili says “the future … is fixed, even though we don’t know it yet.” This conclusion would repeal the very laws of physics Al-Khalili was claiming to honor. The future is dependent on us because, to repeat myself, laws of physics must be applied to boundary conditions to derive a prediction about the future, and those boundary conditions include us.

Modern physics does destroy the traditional “solution” to the “problem of free will”. What these commentators don’t seem to notice is that it also destroys the traditional “problem” of free will. When you notice that your intuitive ideas of time and causality conflict with science, you need to figure out the full consequences of the science, not take one point from science and then re-apply your intuitive ideas. The future isn’t set in stone. It’s set in spacetime. And spacetime is lighter than air.

Free will, part 5 of 5-ish

Laws of nature / Causality / Determinism can be:

(A) Universal, applying to everything

(B) Unidirectional, making for controllers and the controlled

(C) Scientific.

But not more than two of (A)-(C). Causality is unidirectional and scientific, but not universal. Laws of nature are universal and scientific, but not unidirectional. Determinism as imagined in the Consequence Argument is universal and unidirectional, but not scientific. That’s why the Consequence Argument fails.

We think of the past as fixed and the future as open. Some people think science has shown that the fixed past is real and the open future is an illusion, but the truth is almost diametrically opposite. The idea that the whole past is fixed is an overgeneralization. It is a natural, and even rational, inference from our experiences as macroscopic beings, but still a mistake.

Even though (the evidence indicates) the past only depends microscopically on the present, what is advocated here is not a version of Lucretius and the “swerve”. It’s not that we get our freedom from microscopic past phenomena (such as quantum phenomena) in particular. The idea that freedom has to be handed down from past to present is wrongheaded to begin with. If in some particular case, a macroscopic past state did perfectly correlate with our macroscopic present action, that would still not be a problem: that macroscopic past state would then be up for grabs. (Aside for the really nerdy: This is why I am not a big fan of Christian List’s reply to the Consequence Argument, even though it may have a solid point. It concedes too much.)

Sourcehood arguments

An additional group of anti-free will arguments, vaguely similar to the Consequence Argument but different, are called sourcehood arguments. Let me just quote the first premise from the Stanford Encyclopedia of Philosophy article:

1. We act freely … only if we are the ultimate sources (originators, first causes) of at least some of our choices.

This one wears its allegiance to a certain picture of time and causality on its sleeve. Why ultimate source? Why not just source? Because the proponent of the argument mistakenly thinks that physical events are in the general habit of bossing each other around, so that the only way we can avoid being controlled is to conjure something ex nihilo. Hopefully, we’ve covered this ground enough that the reader can see what’s wrong with that premise.

Moral Responsibility

People often do bad things when they could have done better things. Does that mean Retributivism is justified? (Hint: No.) Retributivism, on one definition, is the view that it’s intrinsically morally better that a wrongdoer suffer than that they do not, provided that they could have done otherwise.

Retributivism is not a metaphysical mistake. But in my view, it’s a moral mistake. Instead, punishment is justified when justifiable rules call for it, and discovering those rules depends on free and open moral dialogue among people who will be affected by the rule; people who are intent on reasoning together about how to get along. Others may not care to get along. We need a backstop to enforce livable social rules on those who would otherwise harm anyone who got in their way, and those who are a little more pro-social yet still go off the rails sometimes. But not everyone needs suffering to keep them in line, and those who do should not receive more than the minimum required.

There’s a more humane approach to justice that is common in many indigenous societies, and is making something of a comeback in ours. Here’s part of a transcript of an interview about restorative justice. Michel Martin is a show host, and Sujatha Baliga is a recent MacArthur Fellowship winner who works on restorative justice.

MARTIN: I’m glad you raised that as a crime of violence because I think many people may be familiar with a concept of restorative justice in connection with, you know, teenaged mischief, for example. Let’s say you deface somebody else’s football field before the big game, and they find out that you did it. And the consequence is you have to clean it up. In matters like this, in matters of serious crime and serious harm, where someone’s life is taken, where someone is seriously harmed, what, in your view, is the societal benefit of taking this approach?

BALIGA: Actually, restorative justice works best with more serious harms because we’re talking about people who are actually impacted. In that face-to-face dialogue, you can imagine it not having any heat or any value, really, in terms of the wake-up or the aha moments when we’re talking about graffiti versus when someone has actually entered someone’s home and taken their things, right? That’s a situation that calls for accountability, calls for a direct dialogue where someone takes responsibility for what they’ve done. So, to my mind, restorative justice – and it’s not just to my mind. There’s international data that shows that restorative justice is actually more effective with the more serious harms that people do to one another.

Emphasis added. A humane approach to justice doesn’t depend on the denial of free will or moral responsibility. Quite the opposite, in this case.

The past isn’t your master (part 3 of 5ish)

The law of causality, I believe, like much that passes muster among philosophers, is a relic of a bygone age, surviving, like the monarchy, only because it is erroneously supposed to do no harm.

Bertrand Russell, Selected Papers

Scientific determinism isn’t sufficient for causality, as we pointed out last time. That’s because the laws of nature we actually have allow us to derive the past states from a complete description of the present, every bit as much as they allow us to derive the future from the present. Consider some very simple possible universes called checkerboard worlds (modeled after Carroll [2010: 127]), shown in the following figures.  They have one dimension of time, which will be displayed along the vertical, and one of space, along the horizontal.  To establish conventions, say that time t increases from t=1 at the bottom to t=10 at the top row, and position increases from x=1 at left to x=10 at right.  Discrete spacetime regions can have either of two states, portrayed as white or gray.  Our job as scientists is to come up with a most elegant statement of the rules, or patterns, embodied in the universe.  We can further imagine that after hazarding a hypothesis, more of the universe (more time and/or space) will be revealed to test it. Our first checkerboard universe is C, below.

state(t,x) = state(t-1,x-1) (or state(t,x) = state(t+1,x+1)

The law of nature of C is simple, and shown in the caption. Note that it can be stated as a rule for deriving later-time descriptions from earlier ones, or as a rule for deriving earlier descriptions from later ones. Let’s call that kind of law of nature bidirectional in time. That doesn’t mean that the direction of time make no difference. If we flip universe C in time, around the middle of the diagram, we get C-prime:

state(t,x) = state(t-1,x+1) (or state(t,x) = state(t+1,x-1))

Note that the law is different, in that the state at position x matches the previous state at position x+1 in C’, not the position at x-1. In three spatial dimensions, if we flip all spatial directions at once, physicists call that parity reversal.  Universe C has Parity-and-Time (PT) reversible laws.  The best accounts of the laws of physics of our actual universe,  general relativity and the Schrödinger equation of quantum mechanics, are Charge-Parity-and-Time (CPT)-reversible.

It’s worth staring at picture C’ and asking:  does row 8 make row 9 have gray cells at positions 4 and 8?  Or does row 9 make row 8 have gray cells at 5 and 9?  Or does the whole metaphor of physical states bossing each other around lose its grip here?

Let’s look at a checkerboard universe that doesn’t have bidirectional laws. This one has four possible states for any spacetime location, which will be represented as white, light gray, dark gray, or black.

irreversible dynamics and information loss

A black pattern moves to the left (lower x) with time, but ends if it collides with a dark gray column. Similarly, a light gray pattern ends if it collides with a dark gray column. And a dark gray square can appear “out of nowhere” (that is, when no other dark gray square is within +/- 1 spatial location) – at least when the local neighborhood contains only white squares. It looks like universe M might contain at least one probabilistic law: something like “if x-1 through x+1 are white squares at t-1, then the probability of dark gray at t,x is 0.01”. If not for this last feature, universe M would have been unidirectionally deterministic. Information about the past would be lost, but the future could still be derived from the present. But with the addition of the probabilistic law, universe M loses information in both temporal directions.

M is for macroscopic. The world we can observe with our unaided senses, and which we are accustomed to acting on and caring about, is like M. In the human-scaled world the same effect can come about from multiple causes, and different results can issue from the same situation. On the latter point, to vary our earlier example, a cup of cool water could be caused by leaving a cup of cool water in place, and no heat exchange taking place. Or it could be caused by leaving a cup of hot water with some ice in it for a long time, instead.  So, tracing from the same state (same in macroscopic terms) and going backward in time, different possibilities appear, which all converge on the same present state. And likewise forward in time: the weather, and human decisions, are notoriously unpredictable. We can offer Alice the choice of lunch destinations, and sometimes she picks Mexican and other times Korean, without any observable difference (such as how long it’s been since her last visit to these places) to explain it. Her futures diverge from the same macroscopic present state.

It’s the convergence of macroscopic causality – the fact that the cause (ice water left in the room) guarantees the effect (cool water) but not vice versa – that leads to the idea that the cause is master, and the effect its slave. From our everyday experience, we infer that there is a power differential which is explained precisely by time-order: the past has power over the present, which has power over the future, in a one-way chain of relationships. And that’s a reasonable inference to a simple and elegant theory which neatly fits the macroscopic data – but it’s wrong, as our best theories of microphysical processes reveal. It’s lower entropy, not being in the past as such, which explains why different past states converge on the same macroscopic present state. (More on that next time.)

When someone tells us that the divergence from the present state into multiple future states is an illusion, but neglects to tell us (or notice) that the convergence from past to present states is also an illusion, they’re telling half truths. Half truths can be misleading. This one is.

The Future-Rewound Argument

“I can prove you don’t have free will,” says your strangest friend. “If you had free will, that would mean you’d be able to do something different, even keeping all facts about the future beyond that act fixed. So for example, you think it was up to you where you took your last winter vacation. But if we hold fixed the fact that you were in New York on December 31, and rewind the movie of the universe from there, we find that necessarily, you arranged to travel to New York earlier. So in fact, you had to arrange to travel to New York.”

That’s a crazy argument, which no one would make. The crazy is easy to spot, it’s the idea of keeping all facts about the future beyond that act fixed. You shouldn’t keep those facts fixed, because they are not independent of your decision. But in a universe of bidirectional-in-time fundamental laws, the complete (microscopically detailed) past state of the universe is also not independent of your decision.

But many future facts, like being in New York, are not only not independent of your decision, they are caused by your decision. Causation involves an additional condition: a one-way relationship from cause to effect. Maybe it’s only this one-way causation from your decision to the future that frees you from the need to “keep fixed” those future facts? No: a symmetric relationship will suffice. We can see this in the next two thought experiments.

Self-Referential Pie Chart

inspired by Randall Munroe, XKCD comic (hat tip: Ismael 2012)

The pie chart makes two statements, both of which are true, and it has two pie slices of different size. The size of the reddish slice doesn’t cause the corresponding statement to be true in an asymmetric way: the reddish slice being the size it is, is identical with the truth of the corresponding statement. Once we have a convention that the color of a slice stands for the portion of the chart which is that color, we don’t even have to leave room for a statement written in the same color-range.

Readers are invited to make their own self-referential charts. Be careful in sizing portions and choosing colors: you wouldn’t want to get it wrong! (In the original XKCD comic, Randall Munroe makes his pie chart only partially and indirectly self-referential. So he actually did need to be careful. I call self-nerdsniping.)

The same logic of self-reference that frees us, in this chart-making, from the need to match an independent reality, also applies to our relation to the past under time-symmetric determinism.

Betting on the Past

In my pocket (says Bob) I have a slip of paper on which is written a proposition P. You must choose between two bets. Bet 1 is a bet on P at 10:1 for a stake of one dollar. Bet 2 is a bet on P at 1:10 for a stake of ten dollars. […] Before you choose whether to take Bet 1 or Bet 2 I should tell you what P is. It is the proposition that the past state of the world was such as [to correspond, according to laws of nature, to your action to] take Bet 2.

Ahmed 2014, p. 120

If we take Bet 2, we pocket a dollar. Our usual ignorance about which present states relate to microscopic past details has been removed, thanks to the logic of self-reference. Instead of trying to control a specific macroscopic past event – which is how we usually think about “affecting the past” – here we refer to a present macroscopic event, our taking Bet 2, and work backwards to refer to a widely scattered set of past events, down to the microscopic details.

It’s vital that proposition P is about you. If Bob’s proposition is about what Alice will take when offered this bet, it no longer makes sense to take Bet 2 unless you are Alice. What is up to you depends on who/what you are, including where you stand in the universe. This shouldn’t be surprising.

You might wonder how Bob is supposed to know that the past state of the world was such as to lawfully correspond to your taking Bet 2. But that is easy, if we suppose that Bob is a scientific determinist. He will take our choice as sufficient evidence. Does this mean that we only care about the future, i.e. Bob’s reaction? No: we are honest bettors, who want to take Bob’s money, but only by genuinely satisfying the winning conditions of the bet.

Let’s go back to those counterfactuals. What would happen if we had taken Bet 1? We would have lost a dollar, that’s what. The experiment can be repeated as many times as you like: it would support the hypotheses that “if you had taken Bet 1, you’d lose money” and “if you had taken Bet 2, you’d win money”. Normally, experiments don’t have logically foreseeable results like this; we normally need to know what the specific laws of nature are, not just that they are deterministic. But apart from that, these experiments support “would” statements just as other experiments support more ordinary statements such as “if I dropped this cup, it would fall.” (Remember, even well grounded scientific laws and meta-statements (like determinism) about laws can be supported or undermined by experiments.)

If we can show in more detail that there’s no need to posit an objective Power Hierarchy of Time in which earlier times rule over later ones, then counterfactuals can reach into the past just as easily as into the future. This doesn’t mean that we can change the past, as if some particular past time could be one way – Kennedy was assassinated on Nov 22, 1963 – and then be another way – Kennedy retired after two full terms. Nor does it mean that we can affect the past, if “affect” is a causal verb. It just means that if we had taken Bet 1, we would have lost a dollar. The fact that the consequent follows from the antecedent plus the natural laws, seems like a sufficient reason to accept that counterfactual.

It’s worth noting that even under time-symmetric determinism, the proponent of the Consequence Argument has one last-ditch option to preserve premise

(2) The distant past state of the universe is such that, for every action A you could take, if you did A, that past state would still obtain.

They can assert as an additional premise that there is only one action you could take: the one you did take. So in other words, they simply assume you have no options – they don’t need no stinking reason! This eliminates the Consequence Argument in favor of a Consequence Assertion. There is nothing to recommend such an assertion.

Next up: we show in more detail that there’s no need to posit an objective Power Hierarchy of Time in which earlier times rule over later ones. Hint: entropy explains the irreversible behavior of macroscopic processes. Second hint: the scientific and engineering approach to understanding systems explains how we understand causality.


Ahmed, Arif 2014. Causal Decision Theory and the Fixity of the Past, The British Journal for the Philosophy of Science 65/4: 665–85.

Sean M Carroll, From Eternity to Here: the Quest for the Ultimate Theory of Time. New York: Penguin, 2010.

Ismael, Jenann. Decision and the Open Future, in The Future of the Philosophy of Time, ed. Adrian Bardon. New York: Routledge, 2012.

Munroe, Randall, xkcd: Self-Description.

Pearl, Judea. Causality: Models, Reasoning, and Inference. New York: Cambridge University Press, 2000.

Free will, part 2 of (5-ish)

As we said last time “alpha is unavoidable for you” means “For every action A you could take, if you did A, alpha would (still) happen / be true”. A key concept here is a would statement, which logicians call a “counterfactual conditional”. For example, if I had written that logicians call a would statement “the cat’s meow”, you would think I was joking. The term “counterfactual” is a bit misleading because there can be would-counterfactuals with factual antecedents. For example if I had written that the Consequence Argument was formulated by Peter van Inwagen, you would have read the name Peter van Inwagen. And I did; and you did. What the would statement adds, beyond the simple statement that I did so write and you did so read, is the idea that there’s a robust connection between those things. A counterfactual is a bigger claim than the “if” from propositional logic (which logicians often symbolize with “⊃” — so A ⊃ B simply means that it’s not the case both that A is true and B is false.) Note that counterfactual antecedents and consequents (the “if…” and “would…” parts, respectively) range over processes, events (including boring events like a particular state obtaining at a particular time), and actions.

The premises of the Consequence Argument that we’ll question are (and here let’s spell out the counterfactuals contained in the shorter versions):

(2) The distant past state of the universe is such that, for every action A you could take, if you did A, that past state would still obtain.

(3) The laws of nature are such that, for every action A you could take, if you did A, those laws would still obtain.

And we won’t question premise (1) from the last post, nor the formulation of scientific determinism from which it follows, but we will take a good hard look at that formulation. It turns out not to say some of the things that we might on first glance think it says.

Laws of nature

As I mentioned last time, premise (3) is controversial among philosophers. There’s a dispute over what kind of thing the “laws of nature” are. On the view called the Best Systems Analysis, laws of nature are just a sort of summary of facts. This view is held by the most zealous fans of Occam’s Razor — or at least, that’s what I think they would claim — because it avoids treating laws of nature as a deeply separate category of facts. (Occam’s Razor says “Entities should not be multiplied without necessity.”) Terrance Tomkow has a good explanation of the Best Systems Analysis at: and

The Best Systems Analysis has a model in Algorithmic Information Theory, for which a very crude model is a .zip file, such as you might create from a .txt document on a computer. The .zip file contains compression rules plus compressed data (and the program that reads and writes zip files, say 7zip, contains additional compression rules). The compression rules (including those in the zip-making program) are like the laws of nature, such as the mass and charge of an electron; the remaining data is like the remaining facts, such as the locations of electrons at particular times. Different programs, say 7zip vs the Windows file compressor, might make somewhat different decisions about how to divide up the totality of information in a text file into “compression rules” vs “raw data”. And of course, if you put a different text file into the zip program, you typically get output containing both different “rules” and different “raw data”. For example, if I have a text file where most lines consist of a lot of spaces, the compressor program might make a rule where one special character represents 9 consecutive spaces and another represents 3 consecutive spaces. Then a line consisting of 13 spaces can be abbreviated with 3 characters. But if the text file instead contains a lot of consecutive z’s and no consecutive spaces, the rules part of the compressed file will contain rules representing z’s instead.

It’s this last point that casts doubt on the immunity of laws of nature to human action. If human actions were distributed differently, the totality of physical facts of the universe would be different, so different “compression rules” might most-efficiently summarize the total physical information. If all that laws of nature are, are just efficient summary rules for physical information, then they depend on all that information: the human related bits included every bit as much as the rest. The individual ground-level facts, including what people are doing, are fundamental, on the Best Systems Analysis. The laws are consequences of those facts, not governors of them.

Now, it would be nice if I could say whether the Best Systems Analysis is correct. But all I can do is register my hazy suspicion that it’s not. (My thoughts on that aren’t even worth setting down.) So it seems we are stuck on this part. But wait! What’s that smell? Yes, it’s the sweet smell of unnecessary work! (Hat tip: Dilbert comic.) There’s a chance we don’t have to decide about Premise 3 of the Consequence Argument, and thus we don’t have to decide about the Best Systems Analysis of laws. We don’t need to evaluate Premise 3 if we can undermine Premise 2 of the Consequence Argument. And we can.

The Past

Let’s look again at Premise 1 of the Consequence Argument, or better yet, at our definition of scientific determinism (abbreviated SD), from which Premise 1 followed:

(SD) Determinism requires a world that (a) has a well-defined state or description, at any given time, and (b) laws of nature that are true at all places and times. If we have all these, then if (a) and (b) together logically entail the state of the world at all other times (or, at least, all times later than that given in (a)), the world is deterministic.

Stanford Encyclopedia of Philosophy entry on “causal determinism”

SD says that the laws plus a complete description can logically entail the state of the world, either symmetrically both into the past and future, or asymmetrically just into the future. But the actual laws of physics that science has given us to this point are time-symmetric in exactly this sense, at least when they are deterministic. Conservation of information in quantum mechanics is a case in point. (There are deterministic interpretations of quantum mechanics, such as the Everett Interpretation, which interpret quantum probabilities as statements of rational expectation in the face of partial ignorance.) Because of conservation of information, the final state of a quantum system plus the environment, after an interaction, must contain the information that the system had beforehand. In other words, from the later state plus the laws of quantum mechanics, the earlier state is logically implied. Scientific determinism is a two-way street.

But now notice: “causality” is supposed to be a one-way street. A cause is not supposed to be itself caused by the very thing it supposedly caused. Let’s make this part of the definition of “cause”: causation is asymmetric, so that “A causes B” and “B causes A” are contraries. It immediately follows that

(Determinism ≠ Causality) The existence of laws of nature that logically entail state B at one time given state A at another, does not suffice to show that A causes B.

Causation is not interdependence, but one-way dependence. For example, a room-temperature cup of water could be caused by leaving a cup of steaming hot water in the room until the temperature equilibrated with the room. Or it could be caused by leaving a cup of ice water in the room for a long time, instead. The effect is guaranteed by the cause, but no particular cause is guaranteed by the later state. Without this kind of asymmetry in the relationship, causality is lacking, as physicist Sean Carroll explains in this 3-minute video. “There’s just a pattern that particles follow,” he says. “Kind of like how the integer after 42 is 43, and the integer before it is 41, but 42 doesn’t cause 41 or 43, there’s just a pattern traced out by those numbers.”

So where does causality come from? I’ll give two answers reflecting different interpretations of “causality” – both of them useful in different ways. On one reasonable interpretation (used by Sean Carroll), causality comes from entropy. On another reasonable interpretation, given by Judea Pearl in his book Causality, causality comes from our division of the world into a system of interest vs exogenous variables.

Now let’s look again at the Consequence Argument’s premise

(2) The distant past state of the universe is such that, for every action A you could take, if you did A, that past state would still obtain.

Is it true? If the “distant past state” is given macroscopically, describing such things as glasses of water and their temperature, then (2) is true, but not adequate for the argument, because (as we’ll see later) the present state of the universe doesn’t follow from the past macroscopic state. But if the “distant past state” is given in microscopic detail, then it is not independent of the present state including what we are doing now.

There is no reason to believe (2), where the states in question are described in microscopic detail. Or rather, there is a reason, but it evaporates once you realize that there’s another explanation for why we never observe the past depending on the present or future. We don’t need to posit a magical “flow of time”, or a universal master/slave relationship between past and future. The idea that the past has power over the future but not vice versa is an overgeneralization from our experience of the macroscopic world: our experience of states and processes large and complex enough for entropy to be well-defined and increasing in only one temporal direction.

All this has gone by way too fast, and there are many points that need further justification and explanation. Along the way, we’ll use modern science to deeply challenge our intuitive conceptions of time and causality, then show how those wrong intuitions about how our universe works have affected our views of the free will “problem”. Scientific determinism isn’t the problem – our misconceptions of it are. The traditional free will problem doesn’t hinge on the definition of “free will”, but of “determinism” and “causality”.

Free will: the argument against (part 1 of 5ish)

Let’s start with some popular versions of what I call “the main type of argument” against free will. Here’s Jerry Coyne, from the conference called Moving Naturalism Forward:

(stolen from Anthony Cashmore) Free will is defined as the belief that there is a component to biological behavior that is something more than the unavoidable consequences of the genetic and environmental history of the individual and the possible stochastic laws of nature.

Jerry Coyne, Free Will and Incompatibilism: Jerry Coyne et al – YouTube, at 2:00

There are two words there that are doing a lot of work: “unavoidable” and “consequences”. The “unavoidable” becomes both more and less clear, in different ways, when Jerry comments on the “stochastic laws of nature” part of the definition.

My definition used to be: If you put yourself in the same situation in the same universe with every molecule in the same place, free will would mean that if you come to a decision point you could make more than one decision. But then I realized that quantum indeterminacy if it acts on the neuronal level could make you make a [conscious and] different decision.

ibid., at 2:22

What gets less clear after this explanation is why the word “unavoidable” is appropriate. when it is hypothesized that human behavior might be different even putting yourself in these highly restricted conditions. And worse, the “same universe with every molecule in place” includes all of you. If something flows from you, that seems an especially poor reason to call it unavoidable. But what gets more clear, I think, is why a non-stochastic (deterministic) view is thought to make behavior “unavoidable”. Genetic and environmental history, after all, can be traced back before you were born. And the universe before your birth doesn’t include you. So let’s forget about stochastic laws of nature at least temporarily, and just get clear on the basic argument, assuming that the laws of nature are deterministic. We will use the scientific meaning (not, say, a theological meaning) of determinism:

Determinism requires a world that (a) has a well-defined state or description, at any given time, and (b) laws of nature that are true at all places and times. If we have all these, then if (a) and (b) together logically entail the state of the world at all other times (or, at least, all times later than that given in (a)), the world is deterministic.

Stanford Encyclopedia of Philosophy

So we’ll assume now that our universe is deterministic in this sense, and formalize the argument against free will. If we need to see if it generalizes to the case of stochastic laws (teaser: we won’t need to), we can check that later. We can interpret the phrase “consequence of genetic and environmental history” (from Cashmore and Coyne) as the logical entailment mentioned in the definition of determinism. And we can add two plausible premises: the state of the past before your birth is for you unavoidable, and the laws of nature are unavoidable. (To save words later, “the past before your birth” is abbreviated “the distant past”.)

Here’s how we’ll understand “unavoidable”: “Alpha is unavoidable for you” means “For every action A you could take, if you did A, alpha would (still) be true”.

The argument we get is the Consequence Argument, a famous (infamous?) argument in modern philosophy. The original formulation was by Peter van Inwagen, but that relied on an inference rule which was invalid. A better version was later constructed by van Inwagen, David Widerker and Alexander Pruss. It goes like this:

(1) The distant past state of the universe, together with the laws of nature, together logically entail your action now.

(2) The distant past state of the universe is unavoidable (for you).

(3) The laws of nature are unavoidable.

(4) If a proposition X expresses a fact unavoidable for you, and X logically entails Y, then Y is also unavoidable for you.

(5) Therefore, your action now is unavoidable for you.

The argument so formulated actually makes premise (4) a tautology, and I want to continue assuming for the sake of argument that (1) is true. But premise (3) is controversial and (2) even more so. We’ll take them up in the next part.


Pruss, Alexander 2013. Incompatibilism Proved, Canadian Journal of Philosophy, 43/4: 430–437

Van Inwagen, Peter 1983. An Essay on Free Will. Oxford: Clarendon Press.

Widerker, David 1987. On an Argument for Incompatibilism. Analysis, 47/1: 37–41.

Free will part 0 of (five-ish)

There are two main sub-topics to the free will debates in philosophy, or three, if you count moral responsibility. But I don’t count it, because people who basically agree about when people have genuine choices and when they don’t, often still disagree about moral responsibility. So let’s call that a separate albeit closely related topic. That leaves two main free will topics, corresponding to two main argument types that advocate the conclusion that you don’t have free will.

You’re here, reading this

The first type diminishes “you” to the point where you don’t exist, or don’t have a will. The second admits (at least for the sake of argument) that you exist and have a will, but claims that you are systematically coerced and enslaved by forces alien to you, so you don’t have a free will. I think the second type is far more influential among the general public, so I will focus on that in subsequent posts. (I’m not discounting the possibility of third+ types, but they’re rare beasts if they exist.)

The “non-existent person/will” argument is plausible only to a few people, mainly those who are in the middle of abandoning a dualistic (“soul vs machine”) view of mind and body, but haven’t quite gotten there yet. To reforming dualists, it often seems like the body or brain can’t possibly have consciousness, will, and so on. But really, either the body does have these features, or else non-dualism has an enormous pile of evidence against it. (Hint: the body does have these features.) As human activity is traced to various brain regions, the fearful (ex-, but not utterly ex-)dualist carves off those parts from “me”. That’s a bad move. As Daniel Dennett says, “If you make yourself really small, you can externalize virtually anything.” Don’t make yourself really small.

A less common reason for the Disappearing Self Trick is a bizarre metaphysics recognizing only the properties of microscopic objects (and/or only micro-particles and not composites) as real. As if there could be no cherry pie unless there were cherry pions: fundamental microscopic particles with an inherently cherry property. Or as if there weren’t large objects composed of small parts. But such restrictive “principles” of what’s real are usually selectively applied, indicating that the real concern is mind-body dualism. Often this is accompanied by accusations that people like me, who find mindful states in the human body, are secret dualists: a feat of projection that would make Donald Trump envious.

And that’s all I have to say about the Disappearing Self Trick. If you need more, Eliezer Yudkowsky has several posts (that’s three separate links) that are pretty good. Up next: an intro to the most influential argument against free will, with highlights for closer scrutiny.