I apologize if this has already been mentioned, but there was a major new study that came out in Science today about the global environmental impact of food production. There are a bazillion studies analyzing food production and the environment, but this is by far the most comprehensive one ever attempted -- a metastudy of over 500 other studies covering 40,000 farms and about 1,000 processors in about 120 countries. So for sheer scale and ambition there are no competitors. Here is the link to the study in Science:

The global impacts of food production

Joseph Poore, professor at Oxford and the leader on the study, told the Guardian unequivocally:

A vegan diet is probably the single best way to reduce your impact on planet Earth, not just greenhouse gases, but global acidification, eutrophication, land use and water use.

A pretty rousing endorsement from an Englishman!

Let me first say that I like that you made this thread. Here's how I think about it:

On issues where the philosophical disputes are sharp, it can certainly help to provide definitions, if for no other reason than to get people to think critically about what ideas they actually hold. A good example of what I'm talking about is the hard problem of consciousness. Everyone and their mother has an "intuition" about what consciousness is, but when people are pressed to define what they mean by consciousness, they recoil into their dungeons and familiar lairs. Another example is with the very concept of philosophy. A lot of people criticize or ignore philosophy because they believe it's a useless endeavor. They rarely think critically about what they actually mean when they talk about philosophy. I define philosophy as a general method of analyzing the nature of the world through logical arguments and empirical observations. I know others might disagree with that definition and that doesn't bother me. At least I have a fairly concrete sense for what I mean when I say philosophy. I think I do philosophy every moment of my life when I am required to think hard about something: whenever I play chess or write a piece of code or critique something I just read.

I think you can still do good philosophy without providing a definition for literally everything, but when controversial terms and issues come up, then yes everyone could benefit from trying to clarify their thoughts by coming up with definitions. Then you can begin to demarcate your particular problem from other issues in the world, and maybe stand a chance of providing a satisfactory solution.

David Johnson had a great takedown:

Naturalism Undefeated: A Refutation of the Argument from Reason

As you implied yourself, there is never a "last word" on any philosophical subject. By "refuted" I mean both that the argument has been shown to be faulty and that its implications are rejected or not accepted by a substantial majority of professional philosophers. This widely cited survey from Chalmers showed that 57% were physicalists about the mind. That number will probably go up as neuroscience makes additional breakthroughs. Granted the survey had methodological problems, but the years spent studying this issue do not give me the impression that the argument holds much currency among professional philosophers.

I don't think it's inaccurate to say that the canonical versions of the argument from reason, as proposed by Lewis, have been completely refuted. Sure bad arguments resurface in all kinds of different ways. They will never go away entirely. The ontological argument is still going strong in certain theological circles.

I think your opening question is the most important one: can science demonstrate in principle that only physical things exist?

No I don't think it can and I don't think it should try to, nor should that be the standard by which someone can reasonably believe that naturalism is, broadly speaking, the most accurate description of reality. I think a combination of sound theoretical arguments and the "weight of the empirical evidence" is good enough for believing that naturalistic explanations are sufficient to describe what we see, notice, and measure.

I have not read it entirely, but I am familiar with the gist of the argument. If everything is just physical causes, then humans cannot have intentions and desires. But the statements about mechanisms are themselves expressions of intent, hence contradiction.

I also don't know if you are aware that this argument has been mercilessly refuted by now, to the point that later on Malcolm himself had to drop it in favor of other fantasies about why the mind cannot be physical. Charles Taylor had a brilliant takedown in 1985. He argued that it is not the goal of neuroscience to provide an a priori explanation for wants and desires separate from the organisms to which these conditions apply, which is the kind of linguistic game Malcolm was engaged in. The goal of neuroscience, in the context of our debate, is to explain the physical relations between brain states, bodily states, and the external world. As Taylor writes:

We could indeed never show why wanting peanuts is followed by trying to get peanuts, but we could show why this behavior follows [some state] Px; and this contingent nomological regularity would be what underlies our present use of the concept "wanting peanuts."

Once you have those relations, then you can apply conceptual metaphysics like, "Johny wants to eat an apple." And you can take that to mean: the world has produced physical configurations where Johny is thinking very hard about an apple. Maybe even a configuration where Johny is hungry, the apple is the only thing around, etc. Maybe one where Johny saw something, recalled a childhood memory stored in the brain, then started thinking of an apple. You get the idea.

As for science and metaphysics:

I do think it's necessary and important for science to use some level of metaphysics in its analysis of the world. Otherwise the world just doesn't make sense. To me metaphysical ideas are useful mental constructs that help organize and process information about reality, which would otherwise be too complicated to barely grasp. Scientists who think they can do without metaphysics are misguided. They do metaphysics without even realizing it. After all, no car driving down the road has a shiny yellow vector pointing out the front! Vectors are useful mathematical abstractions, a way for the mind to organize concepts like speed and direction.

On the other hand, metaphysics has often flirted with becoming totally detached from empirical reality, depending on who was using it. And that's when you start getting things like angels, Platonic realms, and Jedis. So I think philosophers also need to be careful in how they use metaphysics. But I get that the main problem now is the stereotypical ignoramus, like a Lawrence Krauss, who does not seem to understand the fundamental value of philosophy.

Wayfarer:

I contend that the predictive capacities of logic and math are entirely explainable by seeing them as emergent properties of human cognition. Some fundamental work has already been done along these lines by neuroscientists like Anil Seth, Karl Friston, and Giulio Tononi, among many others. Anil Seth's predictive theory of consciousness addresses the major points that you raised. He literally sees the brain as a biochemical prediction machine. Now I don't claim that these theories are finished or that the puzzle of conscious experience has been solved, but there has been enough fundamental progress to at least begin to understand these issues and to see how they concretely relate to each other.

You mentioned the limits of evolutionary biology. That's funny, because hundreds of years ago people thought that the explanation of life required a soul or an 'animating' force beyond the body that was in control of our motion. Then biology, chemistry, and physics had their say and no one (who should be taken seriously) believes that anymore. The useless effort to stall the progress of neuroscience now is very much reminiscent of that: there is this deeply held belief that people just cannot possibly be physical systems subject to energetic constraints! The thought alone to some is horrifying. And yet, that's exactly what we are. To me that's worth celebrating: it shows that we too are a part of this big beautiful family called nature.

You are obviously a fan of the history of philosophy, in a morbid kind of way that holds a tragic nostalgia for what has been lost. But cheer up, not everyone back then was totally clueless. Here is good old Lucretius in the Nature of Things:

Since the Nature of the mind and spirit, as we learn, is basically a part of a human being - then return
The name of harmony to the musicians.

Now pay attention here:
I tell you mind and spirit are bound up with one another,
And that together they combine to form a single nature.

Impressive realizations for someone writing so long ago. Now he got many things wrong too in the poem, but the things he got basically right are just astounding. And just for kicks since I have the book open:

All in the void beneath our feet lies open to our sight,
Such revelations and I'm seized by a divine delight,
I shiver, for due to your power, Nature everywhere
In every part lies open; all her secrets are laid bare.

Is a physical mental state a contradiction? To truly argue that, you would need to provide your understanding of the word "physical." Have you automatically defined "physical" as everything that exists outside the mind or the brain? If so, then it's a contradiction just by definition, which doesn't bother me in the slightest, because that definition is nonsense and no one with a few brain cells should use it.

Here's an actual contradiction:

How do you address the epistemological problem of Benacerraf? How does the transcendent Platonic realm communicate with the human mind? How does the mind gain access to the rational treasures of the "world beyond" if not through physical causation?

Yawn. You and I rehashing this debate on another thread is pointless.

Mathematical ideas are mental constructs in the brain. They are physical mental states. How do I know? The last 100 years of neuroscience and all that jazz. Where did the mathematical ideas come from? From the interaction of the brain with the external world. Why do they have predictive power? Sometimes they have predictive power because they do a good job of approximating the real interactions of the physical world. Other times certain math systems may do a poor job of approximating reality. Then human brains interacting with the external world and other brains come up with new math ideas (ie. develop new mental states that can better process the information they're getting from the world). Outside a series of organized mental states, math statements can also exist in symbolic expressions on a particular medium (like an equation written on a t-shirt). Bla bla bla we already played this game and you lost.

It's all physical.

Oh yeah Tom is wrong. I just gave an example above of a purely deterministic differential equation that is not invariant under time-reversal, and this equation describes actual physical systems experiencing friction or drag. Easy.

I just joined this conversation on the fly so I apologize if I don't understand everything right away. Eventually what I want to do here is explain why symmetries are important and place them in a proper mathematical and ontological context (explain why physicists use them and what they mean and don't mean).

Before I get to that, let me address this issue of initial conditions. One thing that confuses me about this debate is the idea that you need any kind of "condition" on a differential equation for the solution to exhibit time-reversal symmetry. Suppose I have a simple differential equation:

dy/dt = t

The solution is y(t) = (t^2 / 2) + C, where C is a constant of integration. If a physical system is described by this equation, then it exhibits time-reversal symmetry even without me specifying anything about initial conditions. The main reason why you would specify an initial condition is to get a unique solution. So if I told you that y(0) = 1, then we would conclude right away that C = 1 (just plug t = 0 in the equation for y). So maybe I'm just slow today but I don't really get what this debate is about: whether an equation is invariant under time-reversal depends on the terms of the equation, not on the initial or boundary conditions associated with the equation.

The fundamental reason why we care about time-reversal symmetry in physics is because it's associated with equilibrium conditions and the conservation of energy. There is a beautiful result in classical physics by Emmy Noether, called Noether's theorem, which states that any continuous symmetry is associated with a corresponding conserved quantity. So if an equation for a physical system exhibits time-reversal symmetry, then the energy of the system is conserved. If it exhibits translational symmetry, linear momentum is conserved. Rotational symmetry means angular momentum is conserved. Gauge symmetry in electrodynamics implies that charge is conserved. This fundamental idea has also been extended to quantum systems in different ways, so the basic idea is not just a classical result. Whether these relationships represent something bizarre and fundamental about nature or whether they are just amazing mathematical connections is still up for debate.

What do physicists do with these results? One thing they do is use experiments to find systems where these quantities are conserved or not, and then they write down an equation that preserves or violates the underlying symmetries. If a system violates a symmetry, that's associated with cool things happening: perhaps the system starts interacting with other systems and loses or gains energy through those interactions. The boring equilibrium conditions give way to something more dynamic. In these kinds of symmetry-breaking Hamiltonians, there is usually a term in the Hamiltonian which acts to break the symmetry under some reversal. So if a system's Hamiltonian changes under time-reversal, then the Hamiltonian is not conserved, which is physically interpreted as the system interacting and forming correlations with other systems. The integer quantum Hall effect is a famous example of a system that breaks time-reversal symmetry. By contrast, the invariance of the Hamiltonian under some transformation is often seen as a sign that a system can be capable of preserving some really interesting feature.

These methods are so powerful in condensed matter physics that entirely new states of matter have been predicted just from writing down an ingenious equation that either preserves or violates a symmetry. Then the experimentalists go and look to find the corresponding system, under the energetic or dynamical constraints implied by the equation.

I think a limiting aspect of this debate is the automatic, almost innate assumption that the laws of physics are always invariant under time-reversal. But if you model dissipation and friction in Newtonian mechanics with a velocity-dependent component, the way it's usually done, then invariance under time-reversal goes away. Like so (in a 1-d system):

F = m ( dx^2 / dt^2 ) - k dx/dt

Clearly F is not the same if I take t to -t. This matters at a macroscopic level because we do have friction, collisions, vibrations, and other dissipative phenomena, which are collectively responsible for the irreversibility of macroscopic events and interactions. Dissipation can be related to entropy since all irreversible phenomena generate some useless heat and increase the combined entropy of the system and the surroundings.

Acceleration does not explicitly appear in the formalism. The time derivative of momentum (equivalent to the force) is set equal to the partial derivative of the Hamiltonian with respect to position, which reduces to the negative gradient of potential energy.

I don't understand that question. The canonical coordinates evolve according to Hamilton's equations.

Also I don't know what Tom means when saying that the acceleration is "captured" by the Hamiltonian. The canonical coordinates of the Hamiltonian formalism are position and momentum. Maybe Tom means that the time derivative of momentum in Hamilton's equations reduces to the second law?

The Hamiltonian is just the total energy of the system, good old T + V.

Some technical points for Tom and Metaphysics Now to consider:

Equilibrium thermodynamics does not model how entropy changes in time because entropy is by definition a state function that is only defined...at equilibrium. Modern thermodynamics, or non-equilibrium thermodynamics, handles how entropy can change in time, but there the definition of entropy is a bit more controversial.

Differential equations are usually deterministic (ordinary) or stochastic. The Schrodinger equation is an example of a deterministic equation: it tells you the future value of the wavefunction for all time once you have a potential energy source and initial conditions. The Langevin equation is an example of a stochastic differential equation. It looks a bit like this:

Langevin = Some average drift term + Some (usually) Gaussian diffusion term that models uncertainty and interactions

Stochastic equations like this one have either strong or weak solutions. The strong solutions are guaranteed to be unique for a given set of initial conditions, as famously proved by Ito. But the weak solutions only have to satisfy the constraints of a special probability space, so they are not "unique" in the traditional sense we know from ordinary differential equations. This can lead to the amazing result that the same initial conditions do not yield the same final answer using intensive computational algorithms (numerical solutions).

Newton's second law is one formalism that specifies the dynamics of a classical system. It is a second-order differential equation. To solve it you need the position and velocity of a system at some given time t. You do not have to specify acceleration to solve the second law.

I don't mean to suggest anything about what "the state of reality is like" when I say all this. I'm staying out of the metaphysical debate. Just wanted to mention these points for your consideration.

Maybe because he wants to learn more about the physical structure and interactions of the brain. He's a neuroscientist. Seth would say that the fact that we're living organisms, and the brain evolved to accommodate our needs as living beings, is what makes it special.

I would recommend that you watch his video. You are starting a pathetic war over nothing. I don't have the answer to every question you can pose while flaming the Internet. I posted a video so people could watch it and maybe learn something.

Seth is not suggesting that consciousness is caused exclusively by neurons. He would say that consciousness emerges from the dynamical interactions between the brain, the body, and the rest of the world. The exact mechanisms are still under study.

I'm not defending his understanding of the hard problem. But I do think people need to engage more with this issue beyond just considering the metaphysics of the hard problem, which is pretty much the only thing George has done in this entire thread.

Have you read Karl Friston? He touches on similar themes to what you are describing.

The free energy principle: a unified brain theory?

This push to characterize the global state of the brain through free energy borrows heavily from thermodynamics and also condensed matter theory, where free energies are often used as order parameters that define the macrostates of different phases of matter and energy.

George,

I wanted to bring to your attention the following Youtube video by the British neuroscientist Anil Seth:

The Neuroscience of Consciousness

It's a great video because he does some really eye-popping live demonstrations and reviews our current state of experimental knowledge on the issue. Seth considers the "hard problem" too metaphysical, so he says he's more interested in finding and categorizing the neural correlates of conscious states. He has a theory of consciousness in which conscious experience is essentially a predictive process resulting from the body's dynamical interaction with the world.

I am recommending this video to you and everyone else not because I hope to convert you to my cause, but because I hope that seeing this video will get you to think about new issues that you may not have considered before.

Dr. Seth ends the video with two quotes that parody Descartes:

Conscious selfhood emerges because of, and not in spite of, our beast machine nature.

I predict, therefore I am.

You really need to look up property dualism. That's pretty much what you're describing, and as I and a few others have noted, your position here is very difficult to distinguish from certain versions of materialism. At least you're not an eliminativist, which I always think is a big hurdle to clear in this minefield of a subject, but you're still basically describing a materialist, naturalist solution to the mind-body problem. Congratulations George, you're finally waking up from the Matrix.

Your Platonic nonsense certainly isn't true.

Do you have a point to make, or are you just going to repeat yourself?

It is quite manifestly obvious by now, after a century of empirical research, that consciousness is absolutely a physical product of material entities.

"Something and above" is philosopher's talk that means nothing. I have told you that superconductivity is an emergent physical state, and that emergent states result from the collective interactions of microscopic or mesoscopic parts.

Aaron,

Your interpretation of superconductivity as an identical feature of some quantity of oxides is total nonsense that no physicist would endorse. Superconductivity is the absence of electrical resistance; it is an emergent property of certain materials under special conditions. The superconductivity of the material cannot exist apart from the material, but it is wrong to conclude from this that the superconducting state is equal to the material itself. Likewise, consciousness is an emergent subsystem of the body under certain conditions.

The terms used to describe qnything is just arguing over semantics. The point is that conscious mental states can be physically distinct, and still physical (ie. subject to energetic constraints in one way or another).

Exactly right. George saying "different and distinct" means nothing in the context of this debate, because we all acknowledge conscious mental states are different than their corresponding neurons.

You basically sound like a property dualist, which is not inconsistent with materialism. It's inconsistent with reductive physicalism. There's nothing "new" about your ideas. Don't flatter yourself.

You've reduced naturalism to belief in evolution. That's nonsense. Naturalism is a broad worldview that states only natural entities, interactions, and causes exist. Naturalism is entirely consistent with materialism. You can't really claim to reject materialism and support naturalism.

Furthermore, your dualism does not escape the epistemological problem. I pointed this out. You totally ignored it. Sounds about right. Do let us know when you move from the new dualism to the old trinity.

The thing I admire the most about you George is that you are perfectly happy to live with glaring and untenable contradictions. You are not a materialist, but you support naturalism (because of course there's a huge difference!). You cite people who disagree with you, and claim that they agree with you!

The finest example of what philosophers may call, "bullcrap." Enjoy your day.

You've converted me to naturalism George! We agree now.

I'm done with this debate. The rest of you have fun.

Fine the joke's on me. Naturalism has won instead.

I am definitely not going to start a definitional war over physicalism, materialism, and naturalism. It's a war with no end.

The mind is natural

I will take this as some measure of agreement on the issue. I don't think our positions on the issue are very far apart at all. We may even have more in common than we let on during this debate.

To say that something non-physical emerges from something physical is either a contradiction or an equivocation on the meaning of the word "emergence," which in this context was defined as the formation of new physical systems from the collective interactions among smaller physical parts of reality.

It's physics all the way up and all the way down. But the physical systems that emerge in reality, from life to nuclear fusion inside stars, can have very different collective interactions and arrangements of matter. Some systems are strongly interacting, others not so much. Some form under very extreme or unique physical conditions, others are less picky. Hence the reasons for the major apparent differences between them.

How does the nonmaterial interact with the material without being material itself?

Bingo. This is the central problem with all philosophical doctrines that reject materialism. They posit one set of causal principles that exist and work in material reality and another set of causal principles that borrow from material reality but don't exist in material reality. It's just pure nonsense.

This is partly what the epistemological problem by Benacerraf was about, which to me constitutes a successful refutation of Platonic realism (and of dualism by extension). Quentin Smith also talked about this same problem in the context of theistic claims about causation.

What does 'identical' mean to you? Because even I may not agree that the mind and the nervous system are "identical."

2,400 years of Platonist propaganda is not a good a priori reason to believe in dualism, any more than 2,000 years of Christian propaganda is reason to believe in deities and fairies.

I suppose we are. I have no great interest in debating your pseudoscience.

The article reviews his experimental results. Did you not read it? Or more accurately, were you not impressed because it happens to contradict some profound and misguided belief you happen to hold?

On the current status of the issue, refer to the following sources.

1) The book Neuropsychiatry and Behavioral Neuroscience (2003) by Jeffrey Cummings and Michael Mega. On page 4:

Contemporary neuroscience has established a fundamental correlation between brain function and mental activity; the data support the basic monistic premise that human emotional and intellectual life is dependent on neuronal operations. This monistic perspective is associated with a philosophy of materialism.

2) The book Psychology of Science (2012) by Robert Proctor and E. J. Capaldi. On page 462 they quote a long list of major thinkers and neuroscientists that reject dualism, including Antonio Damasio:

The neuroscientist Antonio Damasio (1994) is noted for his critique of Descartes's separation of mind and body, which he refers to as a significant "error" thay has misled many cognitive scientists and neuroscientists. Noe (2010) is also clear that the last 25 years have led a growing number of neuroscientists to abandon the Cartesian dualism of mind and body for an "embodied, situated approach to mind" in which we are "dynamically coupled with the world, not separate from it." Rand and Llardi echo the same conclusion: "To the degree that a scientist subscribes to the still widespread Western belief in mind-body dualism...his or her ability to investigate the relationship between mental events and brain events may be compromised."

3) The book Explaining Abnormal Behavior (2014) by Bruce Pennington. On page 176:

Although modern neuroscience has rejected dualism, it still has to account for how cognitive representations and processes can affect bodily states.

4) The cognitive scientist Benjamin Bergen also explains this issue very elegantly. In his book Louder Than Words: The New Science of How the Mind Makes Meaning (2012), he writes in the Foreword:

For centuries we in the West have thought of ourselves as rational animals whose mental capacity transcends our bodily nature. In this traditional view, our minds are abstract, logical, unemotionally rational, consciously accessible, and above all, able to directly fit and represent the world.
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I was brought up to think about the mind, language, and the world in this way. And I was there in the mid-1970s when the revolution started. Some philosophers...had already begun taking issue with the traditional view of the mind. They argued that our bodies have everything to do with our minds. Our brains evolved to allow our bodies to function in the world, and it is that embodied engagement with the world, the physical, social, and intellectual world, that makes our concepts and language meaningful. And on the back of this insight, the Embodiment Revolution began.
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It started out with empirical research carried out mostly by analytical cognitive linguists who discovered general principles governing massive amounts of data. Certain computer scientists, psychologists, and philosophers slowly began taking the embodiment of mind seriously by the 1980s. But by the mid-1990s, computational neural modelers and especially experimental psychologists picked up on the embodied cognition research -- brilliant experimenters like Ray Gibbs, Larry Barsalou, Rolf Zwaan, Art Glenberg, Stephen Kosslyn, Martha Farah, Lera Boroditsky, Teenie Matlock, Daniel Cassanto [and many more]...They have experimentally shown the reality of embodied cognition beyond a doubt. Thought is carried out in the brain by the same neural structures that govern vision, action, and emotion. Language is made meaningful via the sensory-motor and emotional systems, which define goals and imagine, recognize, and carry out actions. Now, at the beginning of the twenty first century, the evidence is in. The ballgame is over. The mind is embodied.

Hahaha! You have won this thread!