It seems to me that biology can not be completely derived from physics — Yuting Liu

This statement needs something to hold it up. A fullfledged watertight argument may not be at hand so I won't ask for that but surely you can tell us what led you in this direction.

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In my view the so-called "theory of everything" is slightly hyperbolic. I think the interdisciplinary problem you've identified is a major one. I understand biology has been trying to rid itself of teleology for quite some time since it has a whiff of the supernatural, but life, whatever life is supposed to be, apparently has plans which can't be entirely apprehended by our current understanding of physical processes. This is to say nothing of the cognitive sciences, whose problems are even more abstract, ie. realizability.

I expect it's possible to reduce everything to a collection of physical things in principle, but a metaphysical perspective makes things even trickier than a biological one since there would still be unexplained phenomena requiring physical import, such as causation and the logical imperative of causal closure, which doesn't seem to be the kind of thing observation and measurement can positively verify despite being a crucial aspect of physicalism. Events, facts, states, kinds and properties also seem to present problems of a similar flavor, and unfortunately they're both necessary and invisible.

While I'm confident our species will find a way around these explanatory gaps and generate a decent "theory of everything" with the assistance of computers, that theory in my opinion will likely feature at least one clunky appeal to practicality, where one variable must be substituted manually as required, rather than being the smooth mathematical description we would prefer. However, this is obviously highly conjectural and there are others I'm sure may like to offer a more robust take on the situation.

If a unified theory of physics derives biology, at some point in the derivation, it should say something like there is life in the universe, but it seems possible to construct hypothetical lifeless universes that physical laws all hold up.

If a unified theory of physics derives biology, at some point in the derivation, it should say something like there is life in the universe, but it seems possible to construct hypothetical lifeless universes that physical laws all hold up. — Yuting Liu

Are you saying that life isn't a necessary consequence of known physical laws?

Firstly, given that most, if not all, experts, time and again, remind us of how less than satisfactory our understanding of the universe is, I'd say we're not in a position to make any definitive claims like that.

Secondly, life evolved because it is simply one of the myriad number of possibilities that physical laws allow and it just happens, out of sheer luck, to be actualized in this universe.

You seem to be under the impression that for physics to explain biology, it must always lead to life and that's wrong for the simple reason that the right ingredients for bios (life) need to converge at a single location in time and space and that may not always be possible.

As an analogy, I offer a simple form of fire - a match fire. To light a fire with a matchbox, we need 1) the match and it has to be struck against 2)the striking surface of the matchbox. To light a matchstick both 1 and 2 have to be in the same place and at the same time. If not, we can't light the match.

(Similarly) A world with the same physical laws we know of but having no life could simply be one in which life-conducive conditions didn't gather at one place and not because the physical laws themselves are lacking qualities that can enable life to evolve.


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Physics currently has two theories. The theory of the very small is Quantum Mechanics, and the theory of the very large is General Relativity. A putative Theory of Everything would be a single theory from which these two naturally fall out in the conditions and realms in which they succeed so well as descriptions. It is difficult, because they are incompatible, so at least one of them is wrong in some very subtle way.

Whether or not the possibility or necessity of life would also fall out of such a theory is also unknowable but unlikely. But the colloquialism "Theory of Everything" should not fool anyone into thinking that if we only had the formula, there would be no more problems or mysteries in the world.

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It seems to me that you are rather arbitrarily drawing your partition at biology. Why not chemistry, for example? Or meteorology? Or just different areas of physics, such as quantum mechanics vs. hydrodynamics? Just like biology, all of those other sciences have distinctive ontological or nomological commitments that are not shared by other sciences. In a few cases a reduction can more-or-less be achieved for some special cases, but by and large these sciences are, for all intents and purposes, autonomous.

Due to Born–Oppenheimer approximation and quantum electrodynamics, the reduction of chemistry to physics is quite successful. However, it's less obvious whether biology or economics also can be explained by physics. Thus the question is raised.

I am not aware of any known difficulties in explaining the behavior of cells in terms of chemistry, or of multicellular life in terms of cells, and chemistry is clearly reducible to physics, so I don’t see any problem here.

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and chemistry is clearly reducible to physics

Last I heard on that topic, admittedly the best part of a decade ago, it was a philosophically contested claim. Back then, there were some philosophers of science looking at how quantum chemistry might provide a reductive bridge between the concepts employed in chemistry and those employed in physics. I was not aware that the debate had been so clearly resolved, do you have a reference article I could read?

chemistry is clearly reducible to physics — Pfhorrest

This is very much in contention and , given your usual thoroughness and scope I'm very surprised you would slip this in in such an offhanded yet apparently authoritative manner. Chemical properties are clearly not reducible to the mechanisms of physics. The entire science of Systems Theory (which offers a much better basis for a fundamental theory) is based on the emergence of new properties governing emergent realms, like chemistry, biology, psychology, etc.

e.g.

"After a long period of neglect, the philosophy of chemistry is slowly being recognized as a newly emerging branch of the philosophy of science. This paper endorses and defends this emergence given the difficulty of reducing all of the philosophical problems raised by chemistry to those already being considered within the philosophy of physics, and recognition that many of the phenomena in chemistry are “epistemologically emergent”."

https://link.springer.com/article/10.1023/A:1009932309197

I intentionally slipped in chemistry in the list of examples, because it is often pointed at as a reductionism success story. But this is at best partially true (as with some of the other examples, e.g. reduction of continuum to statistical thermodynamics and molecular dynamics). When you dig below the surface you find that the challenges in the quest of reduction are daunting even in this case - see for instance Reduction and Emergence in Chemistry article in IEP.

More to the point of the OP, @Yuting Liu singles out the problem of ontological reduction: "the biological distinction of life forms from lifeless forms." But ontological reduction is generally problematic in inter-theoretic relations, and even chemistry-to-QM is no exception (as some works referenced in the above linked article argue). So my point remains that there is nothing special about biology in this regard. The inter-theoretic reduction program is difficult and contentious at just about every level.

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So Kurt Godel has already refuted the theory of everything. You cannot a theory of everything (what he calls "completeness") without having a incoherence at the root of the system. Moreover, you can opt for a coherent system, but it would lack completeness. It's been mathematically proved that a theory of everything is impossible, unless it is likewise incoherent to some measure.

It seems to me that biology can not be completely derived from physics, because physical laws apply to both life and lifeless forms and draws no distinction between these forms. — Yuting Liu

Agree. It is one of the 'myths of the Enlightenment' that the laws of physics can be thought to account for everything in existence. That is one of the reasons that the discipline of semiotics has had to be introduced to biology. 'Biosemiotics attempts to integrate the findings of biology and semiotics and proposes a paradigmatic shift in the scientific view of life, in which semiosis (sign process, including meaning and interpretation) is one of its immanent and intrinsic features' (ref). This is because signs and signal interpretation operates on a plane that is ontologically distinct from physical laws, thereby giving the lie to the original premise of physical reductionism.

The logic here seems to be...

Physics applies to what is alive and physics applies to what is not alive; Therefore physics cannot explain the difference between what is alive and what is not alive.

It's invalid.

They are quite different things.

Having studied some physics and chemistry back in the day, from what I recall chemical properties were explained entirely in terms of the interactions of molecules, which in turn are explained entirely in terms of the physical activity of their constituent particles. Chemical properties and phenomena are aggregate abstractions and so weakly emergent from physical properties, but that still means if you modeled all of the particles at just the physical level you would get the chemical behavior out of the aggregate of them all for free. What about chemistry is supposedly not reducible in this way?

That's literally not my logic whatsoever. That's totally a strawman.

So set it out.

I already did. Any set of propositions can either be 1) incomplete and coherent or 2) incoherent and complete.

That's been proven with mathematics by Kurt Godel. Disagree? Then disprove his theorem. Or prove your own mathematical theorem.

That's not "my logic" that's his. I'm just repeating it. It's all I'm good for. Repeating things other people say to sound smart.

Godel’s theorem is not just about sets of propositions, it’s about axiomatic systems and formal languages. And a description of reality is not necessarily an axiomatic system. A description of reality can be a complete description of reality without being formally “complete” in the sense that matters to Godel.

I think you'd be correct. But that would perhaps make my point. Godel's theorem is related to closed systems, not dynamic open ones like the real world. All the more reason why a description of reality cannot ever be complete. It will always be a description, limited by the human words that are used to describe them and measured by the limited human intelligences behind the computer.

It's confusing the simulation for the simulator. The description for the thing described. The signified for the signifier. The thing-in-itself with the thing being perceived. Blah blah blah.

One thing that's being assumed, that isn't remotely proven to be concretely a thing, is induction. Quine's "Two Dogmas of Empiricism" as well as Hume's "Human Understanding" have shown that induction is just assumed. We assume ceteris paribus. We assume that things behave the same every time, every day, every second. Totally unjustified assumption. In fact, one that scientists have identified as possibly being the case recently.

Totally agree. 100%. The Enlightenment mythology about finding "the laws of the universe" (based on Rosicrucian, Hermetic and Occult mysticism btw) is just that, a mythology. We don't need to posit "laws of the Universe" when all we see are patterns of perception anyway. A pattern is a pattern. Not a law of nature. Just like a turkey ringing a bell and getting fed every day at 11am isn't a law of nature. Just an inference based on a pattern of perception. One day, the turkey rings the bell, no more food for him. Same thing with "laws" of nature.

I actually do believe in laws of nature, but I don't believe our limited human knowledge can adequately account for or describe what those laws are. Our descriptions of those laws are the like the turkey getting fed.

Any set of propositions can either be 1) incomplete and coherent or 2) incoherent and complete. — h060tu

Yeah, not any. Propositional calculus is complete and sound.

What I took exception to was

So Kurt Godel has already refuted the theory of everything. — h060tu

He didn't. Because that theory of everything is not what he was addressing.

You are just being really untidy with your terms.

lol So, Kurt Godel who was one of the greatest mathematicians of the 20th century didn't know propositional calculus existed? Who's more likely to be right?

And yes, theory of everything would fit the definition of a closed system. So, you don't know what you're saying. No reason to continue talking here.

Well, we can agree that there is no point in continuing with this conversation.

What about chemistry is supposedly not reducible in this way? — Pfhorrest

There is a bewildering variety of notions concerning reduction and emergence in the philosophical literature, but I think that the sort of hand-wavy weak emergence that you outline is not very controversial. However, anything stronger or more rigorous than that - such as ontological reduction that the OP brings up - is rife with problems, starting with just setting out the precise meanings of these terms.