I'm a big Sir Arthur Conan Doyle fan, but I'm always bothered whenever this quote surfaces:
> Once you have eliminated the impossible,” the fictional detective Sherlock Holmes famously opined, “whatever remains, however improbable, must be the truth.
This is terrible advice, even more so when mentioned in a scientific publication. This recommendation is the antithesis of what the scientific method is about and a text book example of an argument from ignorance.
You don't pick an explanation because you have run out of ideas to explain a phenomenon, for the simple reason that there might be other explanations you have not considered.
The time to believe something is when there is evidence to back it up.
The key word in that quote is "eliminated". Try this more modern translation:
"Once you have falsified every other possible hypothesis, whatever hypothesis remains is the one we'll promote to a theory."
Holmes' is not saying you get to just make things up - he's trying to explain that instead of trying to prove something directly, inverting your perspective and falsifying as many incorrect interpretations ("the impossible") should always work - even if yo don't understand why.
That quote is an incredibly efficient summarization of the scientific method's core philosophy that (because you can't prove a positive), you falsify wrong hypothesis instead.
> That quote is an incredibly efficient summarization of the scientific method's core philosophy that (because you can't prove a positive), you falsify wrong hypothesis instead.
I disagree and I'll repeat what I said above: this is the antithesis of the scientific method. It's faith based and it opens the door to accepting hypotheses that have zero evidence to back them up. Follow this reasoning and you can just make things up.
In what way is that faith based? It seems to me that falsifying hypothesis until only one remains seems to be pretty scientific. Especially considering that (with regards to science, not solving a murder mystery) that means the world is forever stuck with whatever hypothesis was left at the end because we just didn't think of something else... the same principle or technique can always be used again...
The problem is that, in practice, there is no way to guarantee that you have actually eliminated every possibility. There are ways to constrain the answer within physics, but that doesn't always mean you have an explanation. Besides, within the scientific method (at least in my field of physics) emphasis is placed more on the predictions the answer can make, rather than the simple explanations. Simply eliminating other answers might give you an explanation for a singular case, but it fails to give you the predictive power we demand from all theories.
>there is no way to guarantee that you
>have actually eliminated every possibility
So, what? You just stop once you eliminate the known possibilities?
That last possibility REQUIRES experiment, investigation and thought to verify. If you discover a new possibility then you apply the process again.
The approach is not a one-shot deal, you MUST keep applying it. The current laws of physics are models that we use to explain what we observe and (if the model is good) predict what we might observe.
This by no means implies that that the models describe what's really going on. It is possible to have a model that describes a system that works but is not complete. The deeper we dig, the more we learn.
The fictional quote was meant to describe a deductive approach to investigation, not a rigid method. How often did Holmes dig up new facts and change his mind after eliminating possibilities?
Not really. Proof by contradiction means starting with the negation of the hypothesis you're trying to prove and then reach an impossible conclusion, thereby proving your hypothesis was wrong.
It still involves a rigorous logical reasoning, not accepting something because you're running out of ideas.
If you're defining the technique as not using logic, merely running out of ideas, of course its not logical and wouldn't work in practice. I don't see how what you described as not being 'eliminating the impossible', personally.
> emphasis is placed more on the predictions the answer can make
This is still based on falsifying the hypothesis; prediction is one of the useful tools by which a hypothesis can be experimentally tested. If a prediction ends up being incorrect, you're left with the null-hypothesis. It's entirely possible that the null-hypothesis may not be particularly useful, but it - as Holms said - "must be the truth".
At it's core, the scientific method is simply proposing ideas, and testing them. As zombie-Feynman said. "everything else is bookkeeping"[1].
In the context of murder investigations, perhaps it is easier to form a complete set of possible explanations before applying that principle? That's how I always read it at least.
That's not how it's being interpreted here though. Everything that could possibly happen in the universe does happen, which means that anything which does not happen must be impossible. So we should go find all the rules that make things impossible, and we will be able to predict what will happen from what's left.
That implies that there is a priviledged truth. If two theories are completely indistinguishable by any conceivable experiment, then I would consider them both to be equally "true".
Define "completely different" please.
The two mathematical representation of quantum mechanic were completely different until it was shown that they were equivalent..
Would it be reasonable to claim that if different mathematics give the same answer in all cases, then it is really only different forms of a single mathematic?
They could produce different answers for cases that don't occur in nature. For example you can find many polynomials that go through a given point set (all possible observations you can make) but disagree wildly outside of the point set.
Yes that's what it implies. There's a privileged truth and we don't get to know it. Don't feel bad, though.
You can describe the laws of physics like little gremlins who follow a book of laws that happens to be the laws we know, and the predictions and observations we have will match the gremlins theory.
It doesn't make the existence of tiny gremlins real.
Always love to see new ideas from my apparently-alternate-universe, yet equally-named human copy. What a brilliant mind! Keeps reminding me to seek for deeper answers.
Really a shame that they went for such a strangely click-baity title for what was otherwise a good article, though. This has nothing to do with Copyright and nowhere does the article even attempt to hold up the terrible metaphor.
So if I understand this correctly, this seems a bit similar to how math is built upon a defined set of axioms, which the rest is then derived from.
Given that the axioms they choose are powerful enough, this approach should yield falsifiable results, because if a result turns out to be false, then one of the axioms will turn out not to apply.
I see he's still as obnoxious like always. He makes points, though I'm not qualified to say whether they are valid. I wish he could be more restrained.
That said, if someone like David Deutsch publishes such theories with grand predictions, they deserve criticism.
I scanned the paper and I feel like most of the criticism by Motl is more or less justified. They introduce non-standard notation for things that would probably benefit from a treatment within well established mathematical language. For example their discussion of non clonability of "superinformation", whatever that is, could probably be resolved by working within a non-cartesian monoidal category (which is a standard tool in Quantum logic).
"it isn't easy to ignore Lubos, but it is always worth it" if he could just be a little more on the topic, instead of insulting everyone, his legitimate critiscm would a far greater value.
> According to constructor theory, the most fundamental components of reality are entities—“constructors”—that perform particular tasks, accompanied by a set of laws that define which tasks are actually possible for a constructor to carry out. For instance, a kettle with a power supply can serve as a constructor that can perform the task of heating water .... “You simply say that the task of creating energy from nothing is impossible.”
Looks like someone is getting into OOP:
// Defined
(new Kettle()).boil(new Water());
// Exception
Universe.createEnergyFrom(null)
(yes, I'm joking with this post. But I did find the parallel to be funny)
Well, I'd like to read the published paper. Anyone who is interested in quantum computing comes to his/hers analogies and beliefs of the underlying laws of the universe. The discussions on digital physics have been around since Zuse.
I can't see why they claim that they have found something groundbreaking.
In my opinion, this theory is closer to philosophy rather than quantum mechanics.
It's obviously a speculative theory, but it's a welcomed endeavor, since the field is sorely lacking conceptual frameworks to make sense of scientific advances.
I don't really understand the argument here. It starts to explain a difference between "falsifiable" and "empirical", but then it goes off on an example that I don't understand at all.
Imagining an unobservable multiverse might be a useful way to think about a problem, and it might lead to an elegant way to make predictions, but all we can conclude from that scientifically is "the universe behaves as if there were a multiverse". There's no need to assert that such a multiverse actually exists, and to do so would seem to violate Occam's Razor.
If the article wants to argue that sometimes describing observable behaviour in terms of unobservable entities is neater than the alternative, that's entirely reasonable. But it seems to me that it's trying to argue that the existence of a multiverse is something unfalsifiable that's still scientific, and I don't agree with that at all.
But maybe I'm just misunderstanding something, I don't know that much about theoretical physics after all.
"and to do so would seem to violate Occam's Razor."
That depends on your particular formulation of Occam's Razor. If you're looking at "amount of stuff", it's hard to beat "my experience behaves as if there were a universe".
> “In principle, everything possible in our universe could be written down in a big book consisting of nothing but tasks [and in] this big book will also be encoded all of the laws of physics.”
This is hardly a grand "Theory of Everything" and a lot more like a messy rule book of exceptions and edge cases, that attempts to cover all rules for classical and quantum systems.
It's frequently used outside computer programming. For example, "who was the constructor of the Panama canal" was easy to find with Google autocomplete.
It's used quite a bit in the construction industry.
Indeed, the wording of the article even made me think of type theory and functional programming.
> For instance, a kettle with a power supply can serve as a constructor that can perform the task of heating water.
kettle power_supply water : (water * heat)
> You simply say that the task of creating energy from nothing is impossible.
first_law : (Null -> energy) = _|_
> In principle, everything possible in our universe could be written down in a big book consisting of nothing but tasks
This sounds like an enumeration (eg. a Goedel numbering) of programs, or alternatively of a (program, runtime) quarter-plane.
> The collaborators then go on to define the concept of a “superinformation” medium that encodes messages that specify particular physical states—in this case, one in which copying is impossible
Sounds like substructural type systems and linear (or affine) types.
http://arxiv.org/abs/1405.5563
Edited to steal more screenspace/add context:
Authors:
https://web.archive.org/web/20120402224250/http://193.189.74...
http://edge.org/memberbio/chiara_marletto
You may also be interested in this paper:
http://www.cs.berkeley.edu/~christos/classics/Deutsch_quantu...
Also, http://edge.org/conversation/constructor-theory