Heat vs. Motion
Followup to: Angry Atoms
After yesterday's post, it occurred to me that there's a much simpler example of reductionism jumping a gap of apparent-difference-in-kind: the reduction of heat to motion.
Today, the equivalence of heat and motion may seem too obvious in hindsight - everyone says that "heat is motion", therefore, it can't be a "weird" belief.
But there was a time when the kinetic theory of heat was a highly controversial scientific hypothesis, contrasting to belief in a caloric fluid that flowed from hot objects to cold objects. Still earlier, the main theory of heat was "Phlogiston!"
Suppose you'd separately studied kinetic theory and caloric theory. You now know something about kinetics: collisions, elastic rebounds, momentum, kinetic energy, gravity, inertia, free trajectories. Separately, you know something about heat: Temperatures, pressures, combustion, heat flows, engines, melting, vaporization.
Not only is this state of knowledge a plausible one, it is the state of knowledge possessed by e.g. Sadi Carnot, who, working strictly from within the caloric theory of heat, developed the principle of the Carnot cycle - a heat engine of maximum efficiency, whose existence implies the second law of thermodynamics. This in 1824, when kinetics was a highly developed science.
Suppose, like Carnot, you know a great deal about kinetics, and a great deal about heat, as separate entities. Separate entities of knowledge, that is: your brain has separate filing baskets for beliefs about kinetics and beliefs about heat. But from the inside, this state of knowledge feels like living in a world of moving things and hot things, a world where motion and heat are independent properties of matter.
Now a Physicist From The Future comes along and tells you: "Where there is heat, there is motion, and vice versa. That's why, for example, rubbing things together makes them hotter."
There are (at least) two possible interpretations you could attach to this statement, "Where there is heat, there is motion, and vice versa."
First, you could suppose that heat and motion exist separately - that the caloric theory is correct - but that among our universe's physical laws is a "bridging law" which states that, where objects are moving quickly, caloric will come into existence. And conversely, another bridging law says that caloric can exert pressure on things and make them move, which is why a hotter gas exerts more pressure on its enclosure (thus a steam engine can use steam to drive a piston).
Second, you could suppose that heat and motion are, in some as-yet-mysterious sense, the same thing.
"Nonsense," says Thinker 1, "the words 'heat' and 'motion' have two different meanings; that is why we have two different words. We know how to determine when we will call an observed phenomenon 'heat' - heat can melt things, or make them burst into flame. We know how to determine when we will say that an object is 'moving quickly' - it changes position; and when it crashes, it may deform, or shatter. Heat is concerned with change of substance; motion, with change of position and shape. To say that these two words have the same meaning is simply to confuse yourself."
"Impossible," says Thinker 2. "It may be that, in our world, heat and motion are associated by bridging laws, so that it is a law of physics that motion creates caloric, and vice versa. But I can easily imagine a world where rubbing things together does not make them hotter, and gases don't exert more pressure at higher temperatures. Since there are possible worlds where heat and motion are not associated, they must be different properties - this is true a priori."
Thinker 1 is confusing the quotation and the referent. 2 + 2 = 4, but "2 + 2" ≠"4". The string "2 + 2" contains 5 characters (including whitespace) and the string "4" contains only 1 character. If you type the two strings into a Python interpreter, they yield the same output, -> 4. So you can't conclude, from looking at the strings "2 + 2" and "4", that just because the strings are different, they must have different "meanings" relative to the Python Interpreter.
The words "heat" and "kinetic energy" can be said to "refer to" the same thing, even before we know how heat reduces to motion, in the sense that we don't know yet what the reference is, but the references are in fact the same. You might imagine an Idealized Omniscient Science Interpreter that would give the same output when we typed in "heat" and "kinetic energy" on the command line.
I talk about the Science Interpreter to emphasize that, to dereference the pointer, you've got to step outside cognition. The end result of the dereference is something out there in reality, not in anyone's mind. So you can say "real referent" or "actual referent", but you can't evaluate the words locally, from the inside of your own head. You can't reason using the actual heat-referent - if you thought using real heat, thinking "1 million Kelvin" would vaporize your brain. But, by forming a belief about your belief about heat, you can talk about your belief about heat, and say things like "It's possible that my belief about heat doesn't much resemble real heat." You can't actually perform that comparison right there in your own mind, but you can talk about it.
Hence you can say, "My beliefs about heat and motion are not the same beliefs, but it's possible that actual heat and actual motion are the same thing." It's just like being able to acknowledge that "the morning star" and "the evening star" might be the same planet, while also understanding that you can't determine this just by examining your beliefs - you've got to haul out the telescope.
Thinker 2's mistake follows similarly. A physicist told him, "Where there is heat, there is motion" and P2 mistook this for a statement of physical law: The presence of caloric causes the existence of motion. What the physicist really means is more akin to an inferential rule: Where you are told there is "heat", deduce the presence of "motion".
From this basic projection of a multilevel model into a multilevel reality follows another, distinct error: the conflation of conceptual possibility with logical possibility. To Sadi Carnot, it is conceivable that there could be another world where heat and motion are not associated. To Richard Feynman, armed with specific knowledge of how to derive equations about heat from equations about motion, this idea is not only inconceivable, but so wildly inconsistent as to make one's head explode.
I should note, in fairness to philosophers, that there are philosophers who have said these things. For example, Hilary Putnam, writing on the "Twin Earth" thought experiment:
Once we have discovered that water (in the actual world) is H20, nothing counts as a possible world in which water isn't H20. In particular, if a "logically possible" statement is one that holds in some "logically possible world", it isn't logically possible that water isn't H20.
On the other hand, we can perfectly well imagine having experiences that would convince us (and that would make it rational to believe that) water isn't H20. In that sense, it is conceivable that water isn't H20. It is conceivable but it isn't logically possible! Conceivability is no proof of logical possibility.
It appears to me that "water" is being used in two different senses in these two paragraphs - one in which the word "water" refers to what we type into the Science Interpreter, and one in which "water" refers to what we get out of the Science Interpreter when we type "water" into it. In the first paragraph, Hilary seems to be saying that after we do some experiments and find out that water is H20, water becomes automatically redefined to mean H20. But you could coherently hold a different position about whether the word "water" now means "H20" or "whatever is really in that bottle next to me", so long as you use your terms consistently.
I believe the above has already been said as well? Anyway...
It is quite possible for there to be only one thing out-there-in-the-world, but for it to take on sufficiently different forms, and for you yourself to be sufficiently ignorant of the reduction, that it feels like living in a world containing two entirely different things. Knowledge concerning these two different phenomena may taught in two different classes, and studied by two different academic fields, located in two different buildings of your university.
You've got to put yourself quite a ways back, into a historically realistic frame of mind, to remember how different heat and motion once seemed. Though, depending on how much you know today, it may not be as hard as all that, if you can look past the pressure of conventionality (that is, "heat is motion" is an un-weird belief, "heat is not motion" is a weird belief). I mean, suppose that tomorrow the physicists stepped forward and said, "Our popularizations of science have always contained one lie. Actually, heat has nothing to do with motion." Could you prove they were wrong?
Saying "Maybe heat and motion are the same thing!" is easy. The difficult part is explaining how. It takes a great deal of detailed knowledge to get yourself to the point where you can no longer conceive of a world in which the two phenomena go separate ways. Reduction isn't cheap, and that's why it buys so much.
Or maybe you could say: "Reductionism is easy, reduction is hard." But it does kinda help to be a reductionist, I think, when it comes time to go looking for a reduction.
Comments (27)
Consider two identical flywheels made of iron:
a) starts in room temperature, you apply force and make it spin. b) stands still but you heat it uniformily with several flames.
Suppose that in both cases the same amount of energy has been put into the flywheels.
In both cases the atoms are moving in high speed. Now if you look at the flywheels with an infrared camera would they look the same? This is not a rethorical question.
"the conflation of conceptual possibility with logical possibility. To Sadi Carnot, it is conceivable that there could be another world where heat and motion are not associated. To Richard Feynman, armed with specific knowledge of how to derive equations about heat from equations about motion, this idea is [...] so wildly inconsistent as to make one's head explode."
Shouldn't we distinguish between logical and physical possibility? A world in which heat and motion are disassociated seems to be impossible in a rather different way than worlds in which the law of noncontradiction is false or 7,497 is prime are impossible.
Davis, that depends on whether you take the word "heat" to refer to "whatever actually melts metal" or "microscopic movements and collisions of molecules". See the various discussions of Hilary Putnam's "Twin World" dilemma for more along these lines.
If we look at something with the naked eye and see "plastic" and then look at it again with a super-microscope and see fundamental particles whizzing around, why does the second observation disprove the first or somehow make it an illusion?
Fact 1. This object, when looked at through the naked eye, looks like X. Fact 2. This object, when looked at through the microscope, looks like Y.
Even after you know Fact 2, Fact 1 is still true. Microscopes don't make liars of our eyes. I think the error is in not accepting human limitations to being with.
We are limited. We can only know what things look like through this or through that. But most people forget this and therefore state the two facts as "This object looks like X" and "This object looks like Y" with X != Y, so they think they have to discard one of the facts to avoid a contradiction. Really, they should be careful to state the full context of what they knew each time.
I'm still waiting for someone to tell me where the color is, in a universe made of colorless elementary particles.
Heat has to do more with equilibrium than kinetics.
Mitchell, clearly you haven't looked at http://en.wikipedia.org/wiki/Quarks#Color.
Seriously though, taboo 'colour' from your question. Exactly which bit are you still waiting to have explained?
Ben Jones said:
Seriously though, taboo 'colour' from your question. Exactly which bit are you still waiting to have explained?
I think you're tabooing overzealously. If I have a bunch of red balls and a bunch of blue balls, and ask 5 people to partition the balls into two subsets based on color, I would expect the same result from all 5 people. How do they do it?
I would rather say that the observable consequences of the heat like nature of the universe are already included in the observable consequences of the kinematic like nature of the universe, so heat is redundent in this sence, though still a useful idea.
Relying on the potential existence of an Idealized Omniscient Science Interpreter feels a bit too much like divine revelation for my taste. The difference is rather then saying "Aha! This is what has actually been happening all along." I would say "Aha! This more accurately fits my observations."
Of course it's possible to have heat that's unrelated to molecular motion. Just consider frozen mustard or red peppers.
Question: How much of today's psychology will look to future scientists like attempts to measure the hotness of jalapeno peppers by thermometers?
The heat analogy to consciousness is nothing new.
Chalmers explains and responds here.
Yes, this is old hat. See also my post on Misusing Kripke/Putnam, which explicitly explains why the analogy to 'water = H2O' (and similar a posteriori identities, like heat = molecular motion) is no help to the physicalist here.
Peter, your question doesn't seem to be the right one for illustrating your concern. The qualitative experience of color isn't necessary for explaining how someone can partition colored balls. Ignoring the qualitative experience, these people are going through some process of detecting differences in the reflective properties of the balls (which they subjectively experience as having different colors). We could create a reductive explanation of how the eye detects reflected light, how the brain categorizes reflective intensities into concepts like "bright" "dark" and how the body's mechanics enable picking up and dropping balls. A machine with no apparent subjective experience could sort the balls. However the question of qualitative experience in humans would remain.
We could say "where there is perception, deduce qualitative experience" but this doesn't explain anything. It might help us frame experiments to test for the existence of qualitative experience, but one element of Chalmer's argument is that no such objectively verifiable experiment can be created. It's also hard to come to terms with the idea that our ball sorting robot might be having qualitative experience.
If we are discarding solipsism from our epistemology, on what basis do we do so and is that basis philosophically applicable to discarding the idea that that my qualitative experience might be fundamentally different from someone else's? Just because I can conceive of a world in which what I experience as red is in fact experienced by someone else with no neural/optical flaws as what I would call yellow doesn't make that world logical. I would assume that if the object and lighting conditions are the same and our neural and optical machinery was in good order that we would both experience the same thing that it is to experience red when looking at a red object. To conceive otherwise would be baseless (purely metaphysical with no implications for reality).
[tangent] Hi Brandon, you may find my post on The Problem of Other Minds to be of interest -- note that the usual justification is to argue inductively from analogy (others are externally similar to ourselves, so most likely have similar inner lives).
I think you're right that the diverse experience hypothesis (my red is your yellow, etc.) is 'illogical', at least in the weak sense of ad hoc or less than perfectly coherent/reasonable. It is logically possible, mind you -- there's no reason the would couldn't have turned out that way, if the laws of nature had been different. But we are generally justified in believing that reality is governed by systematic laws. That is, a variation of Ockham's Razor will prevent us from positing unnecessary arbitrary distinctions.
So you're right that the diverse experience view is 'baseless'. But note that it can't be for the reason that it is "purely metaphysical with no implications for reality". For the same could be said of the reasonable (and presumably true) view that in fact we both experience the same colour qualia when looking at a tomato. That too is a 'metaphysical' view with no scientific implications. But it's also plainly reasonable. So, not all 'metaphysical' views are on a par. [/tangent]
I used to lead with the rallying cry of "conceivability is not logical possibility" but after some reflection came to the conclusion that logical possibility is just an arbitrary subset of conceivability and the entire framework of "logical possibility" should be rejected outright. "This is logically possible" carries no weight. It is not a thing. It serves no purpose and has no known use. By rejecting it what exactly do we stand to lose?
I interpret "$SITUATION is logically possible" to mean "$SITUATION can be modeled without any necessary contradictions"; thus, it's logically possible for energy not to be conserved (if we allow to change whatever laws need to change), but not for 21 to be a prime number (within any system of arithmetic like the ones we're used to, but then, if we used another system the relevant object/predicate wouldn't be what we mean by "21"/"prime") - or, more significantly, only one of P=NP and P≠NP is logically possible, even though with my knowledge I can conceive of both.
There's a way you could make the heat=motion concept much clearer to Carnot. When one studies kinematics, one generally makes the approximation that macroscopic bodies are rigid, and the motions of the body refer to center of mass motion, or perhaps rotation about some axis. If you explain that "heat" refers to the motion of the constituent particles relative to each other, I think a scientist of Carnot's day would understand the idea pretty quickly.
I think this sort of thing might be what people mean when they talk about a "bridging theory".
More significantly, only one of P=NP and P≠NP is logically possible, even though with my knowledge I can conceive of both.
Couldn't P=NP and P≠NP both be consistent with the standard axioms of complexity theory (whatever they happen to be right now), in the same way that, say, the different parallel postulates are all consistent with the rest of the commonly accepted axioms of geometry, or the way that the continuum hypothesis is independent of Zermelo–Fraenkel set theory with the axiom of choice?
Richard: Chalmers' argument on the example of heat and his claim that Dennet's conception of a vitalist is imaginary both appear to me to be correct responses to this style of attack on the "hard problem of consciousness".
Unfortunately, the post "Misusing Kripke" seems to me to be horribly confused. You assert that "Nobody thinks that the 'Twin Earth' world Putnam describes is an impossible one. Rather, we still grant the possibility of the world itself, but merely re-assess how best to describe it." and that "we can imagine a world where watery stuff isn't truly water" but in fact, since I actually understand why water is watery and NH3, for instance, is not, can no more imagine a world where watery stuff isn't H2O than I can a world in which a hand isn't five fingers and a trunk. I can vaguely imagine being confused about either in some relevant respects if my brain was manipulated in a fine enough manner, but these sorts of confusions are really pretty much confusions about what constitutes "watery stuff". In the Matrix I could swim in "water" that was not made of H2O, but on earth I can see "water" that turns out to be a mirage too. Both are "watery" in a sense, but not in the relevant sense of being the same sort of stuff as my body or a snowflake are made of. There are things that are "painy" in some senses but not in other senses as well. For instance, the suffering of a character in a movie, of a person's childhood self in their false memories of satanic abuse, or of a practitioner of some sorts of masochistic acts.
Your claim above that "there's no reason the would couldn't have turned out that way, if the laws of nature had been different." is, to my mind, another example of this sort of confusion. You have often pointed out that scientists don't generally understand what philosophers do, but it seems to me that the converse is also true. Might I be so bold as to suggest that both groups are stereotyped on the basis of the different but in both cases relatively silly activities that they both engage in during the 95% or so of the time when they are not both actually doing philosophy? The vast majority of, if not all of, the "natural laws" scientists speak of are not arbitrary. It seems very likely to many prominent scientists (Einstein, Hawking, etc) that they couldn't have been different at all, and certain that they couldn't be changed individually while leaving the universe otherwise the same. It's worth emphasizing that the fact that we find ourselves observing a simple and orderly world (find ourselves to be observations of an orderly world?) indicates that we are not observations selected arbitrarily from an unordered set of observations (whatever that would mean in the general case, Boltzmann Brains are a simple-to-conceptualize special case).
Oh. Yeah. There is that option.
What 'experience'? What properties does this experience have? Let me guess - you can't tell us.
How do you justify your assertion that those experiences exist? How would you convince an honest skeptic that there is more to your perception of mixes of different wavelengths of light than can be explained by referring to the properties of the eye, the signals the eye sends, and the neurology that processes those signals?
Richard:
In an earlier post of yours I find. "I'd add that mostly everyone accepts that the laws of nature are contingent, and that there *could* have been a law according to which lead would transmute into gold. So I'm presupposing that common background."
This is definitely not what I assume. Rather, what I assume is that the laws of nature are, from our perspective, the computations that give our experience as their output. An emergent level of description of these computations is as being "about" various fundamental particles described by different equations, but the equations are all there is to say about the particles. There is no Aristotelian "material" which has the "form" described by the equation of an electron but could have some other "form", say the equation , there is just the equation, what Chalmers calls, I believe, "pure causal flux". Maybe some very very complex equation (more complex than the order of this perceived moment?) could be stated such that *head explodes*...
OK, Zombie Michael writing, brain stuffed back into skull. Michael's head exploded from reading "Water just is H2O, which is why you can't have one without the other (and this is so regardless of whether the physical laws differ. For example, there could be other worlds where water/H2O isn't wet)" in the comments of the "Misusing Kripke" post. It's a far clearer example of what he was talking about. H20 is shorthand for a lot of math, that is to say a lot of logical relationships. Wetness emerges from that math, which can be understood as logic, not just as symbols on paper following symbolic manipulation conventions. It's not just a fact, not the teacher's password, not a pattern to learn to recognize etc. Physics isn't stamp collecting.
By the way, let me take the time here to plug "Thinking Physics" by Lewis Carrol Epstein, not just for Richard but for everyone here who doubts that the logic of physics can be conveyed cleanly without the formalism of symbolic manipulation.
Thinking Physics is Gedanken Physics - I loved that book, tore through it at some point while I was in high school. I never found anything else quite like it.
To those who ask where colour arises from in a colourless world; Wrong Question and Mind Projection bonus!
Imagine an alien civilisation that has, say, fourteen colours. Calling two adjacent ones by the same name would be as ridiculous to them as someone here calling green and yellow the same thing. Still want to claim that 'red' is part of the territory? There are wavelengths, and there is the human faculty to tell them apart at sufficient intervals. Anything else is map only. There is no red.
Say you taste an apple. You know that the sensation you are experiencing is due to chemicals interacting with your taste buds. Do you then say 'I understand why this happens, but clearly this distinctive appley taste is a thing in its own right, which can't be explained by chemical interactions alone. Whither the appleyness?'?
I hope not. I hope you'd recognise that just because evolution has favoured creatures that can recognise certain combinations of chemicals (by remembering them as discrete experiences like 'appley taste'), or certain wavelengths of light, doesn't mean those subjective 'experiences' are part of the territory.
Concession: vision is harder to think about than most sensations, because it seems so tightly bound to reality. Easy to think that what's on the back of your retina is the world.
BTW, Zombie Michael, maybe you can help us. Do you feel conscious? If so, can you tell us whether you're actually conscious or just identical in absolutely every way to someone who's conscious, but lacking that super-special consciousness-juju?
Actually, since we rely upon vision so heavily, we know the most about the 'illusions' it can produce.
No one who has even casually studied how vision works can take "seeing is believing" seriously.
I don't think you need alien civilizations for this. Not all human languages have color words that map 1:1 to English color words. (I seem to recall that the word for "red" in Korean includes what English speakers would call "copper". I could be mistaken.)