Comment author: SilasBarta 02 November 2009 04:09:28PM 3 points [-]

I don't think his way of explaining it is any easier for a newcomer. It doesn't make sense unless and until you already have a firm grasp of the basis for Occam's razor. And if you know how to justify Occam's razor, you already understand why adding details penalizes the explanation's probability.

Furthermore, his idea can't be summarized as "good explanations are hard to vary". It's more like, "good explanations are hard to vary while preserving their predictions".

I do appreciate that you added a summary.

Comment author: mlionson 29 March 2010 12:06:27AM 2 points [-]

I don't think he is saying, "good explanations are hard to vary while preserving their predictions".

As described above the statement "Everyone just acts in his own interest" very easily preserves its predictive power in a multitude of situations. Indeed, the problem with it is that the statement preserves its predictive power in too many situations! The explanation is consistent with just about whatever happens, so one cannot design a test that makes one believe that the statement is certainly false. So it is too easy to vary and hence a bad explanation.

In response to Against Modal Logics
Comment author: Eliezer_Yudkowsky 01 September 2008 03:54:55PM 6 points [-]

What on Earth is evolution, if not the keeping of DNA sequences that worked last time? It's less efficient than human induction and stupider, because it works only with DNA strings and is incapable of noticing simpler and more fundamental generalizations like physics equations. But of course it's a crude form of inductive optimization. What else would it be? There are no knowledge-generating processes without some equivalent of an inductive prior or an assumption of regularity. The maths establishing this often go under the name of No-Free-Lunch theorems.

Comment author: mlionson 24 February 2010 04:27:47AM 0 points [-]

Evolution does not increase a species' implicit knowledge of the niche by replicating genes. Mutation (evolution's conjectures) creates potential new knowledge of the niche. Selection decreases the "false" implicit conjectures of mutations and previous genetic models of the niche.

So induction does not increase the implicit knowledge of gene sequences.
Trial (mutation) and error (falsification) of implicit theories does. This is the process that the critical rationalist says happens but more efficiently with humans.

Comment author: Mitchell_Porter 20 February 2010 12:32:03AM *  1 point [-]

Somehow I never examined these experiments and arguments. But what I've learned so far is to reject counterfactualism.

If you have an Everett camera in your Schrodinger cat-box which sometimes takes a picture of a dead cat, even when the cat later walks out of the box alive, then as a single-world theorist I should say the cat was dead when the photo was taken, and later came back to life. That may be a thermodynamic miracle, but that's why I need to know exactly how your Everett camera is supposed to work. It may turn out that that it works so rarely that this is the reasonable explanation. Or it may be that you are controlling the microscopic conditions in the box so tightly – in order to preserve quantum coherence – that you are just directly putting the cat's atoms back into the living arrangement yourself.

Such an experiment allegedly involves a superposition of histories, one of the form

|alive> -> |alive> -> |alive>

and the other

|alive> -> |dead> -> |alive>

And then the camera is supposed to have registered the existence of the |dead> component of the superposition during the intermediate state.

But how did that second history even happen? Either it happened by itself, in which case there was the thermodynamic miracle (dead cat spontaneously became live cat). Or, it was caused to happen, in which case you somehow made it happen! Either way, my counter-challenge would be: what's the evidence that the cat was also alive at the time it was photographed in a dead state?

Comment author: mlionson 20 February 2010 06:31:35AM -1 points [-]

I think I see where we are disagreeing.

Consider a quantum computer. If the laws of physics say that only our lack of knowledge limits the amount of complexity in a superposition, and the logic of quantum computation suggests that greater complexity of superposition leads to exponentially increased computational capacity for certain types of computation, then it will be quite possible to have a quantum computer sit on a desktop and make more calculations per second than there are atoms in the universe. My quote above from David Deutsch makes that point. Only the limitations of our current knowledge prevent that.

When we have larger quantum computers, children will be programming universes with all the richness and diversity of our own, and no one will be arguing about the reality of the multiverse. If the capacity for superposition is virtually limitless, the exponential possibilities are virtually limitless. But so will be the capacity to measure “counterfactual” states that are more and more evolved, like dead cats with lower body temperatures. Why will the body temperature be lower? Why will the cat in that universe not (usually) be coming back to life?

As you state, because of the laws of thermodynamics. With greater knowledge on our part, the exponential increase in computational capacity of the quantum computer will parallel the exponential increase in our ability to measure states that are decohering from our own and are further evolved, using what you call the “Everett camera”. I say “decohering from” rather than “decoherent from” because there is never a time when these states are completely thermodynamically separated. And the state vector has unitary evolution. We would not expect it to go backwards any more than you would expect to see your own cat at home go from a dead to an alive state.

I am afraid that whether we use an Everett camera or one supplied to us by evolution (our neuropsychological apparatus) we are always interpreting reality through the lens of our theories. Often these theories are useful from an evolutionary perspective but nonetheless misleading. For example, we are likely to perceive that the world is flat, absent logic and experiment. It is equally easy to miss the existence of the multiverse because of the ruse of positivism. “I didn’t see the needle penetrate the skin in your quantum experiment. It didn’t or (even worse!) can't happen.” But of course when we do this experiment with standard needles, we never truly see the needle go in, either.

I have enjoyed this discussion.

Comment author: mlionson 17 February 2010 07:30:04AM -2 points [-]

The Elitzur-Vaidman bomb testing device is an example of a similar phenomenon. What law of physics precludes the construction of a device that measures blood sugar but with the needle (virtually never) penetrating the skin?

Comment author: mlionson 17 February 2010 08:50:41AM -2 points [-]

And if no law of physics precludes something from being done, then only our lack of knowledge prevents it from being done.

So if there are no laws of physics that preclude developing bomb testing and sugar measuring devices, our arguments against this have nothing to do with the laws of physics, but instead have to do with other parameters, like lack of knowledge or cost. So if the laws of physics do not preclude things form happening, we might as well assume that they can happen, in order to learn from the physics of these possible situations.

So for the purposes of understanding what our physics says can happen, it becomes reasonable to posit that devices have been constructed that can test the activity of Elitzur-Vaidman bombs without (usual) detonation or measure blood sugars without needles (usually) penetrating the skin. It is reasonable to posit this because the known laws of physics do not forbid this.

So those who do not believe in the multiverse but still believe in their own rationality do need to answer the question, "Where is the arm from which the blood was drawn?"

Or, individuals denying the possibility of such a measuring device being constructed need to posit a new law of physics that prevents Elitzur-Vaidman bomb testing devices from being constructed and blood sugar measuring devices (that do not penetrate the skin) from being constructed.

If they posit this new law, what is it?

Comment author: wnoise 17 February 2010 07:09:54AM 2 points [-]

That is the most charitable interpretation. I confess that I did not at all think of that.

Of course, given no further details, and hence assuming standard measurement devices and procedures, this sort of thing really is impossible with needles and arms.

Comment author: mlionson 17 February 2010 07:30:04AM -2 points [-]

The Elitzur-Vaidman bomb testing device is an example of a similar phenomenon. What law of physics precludes the construction of a device that measures blood sugar but with the needle (virtually never) penetrating the skin?

Comment author: SilasBarta 30 October 2009 10:03:15PM *  3 points [-]

Okay, I saw in the comments (both here and on the TED site) that Deutsch's point was that good explanations are "hard to vary", but I didn't understand what that means.

So I finally saw the talk (after skipping most of it to get to the explanation of explanation), and it turns out Deutsch just means "lacking unnecessary details" when he says "hard to vary". Which is just the standard point about the conjunction fallacy and how each detail makes your explanation less plausible.

Nothing new here, sorry :-/

Comment author: mlionson 16 February 2010 11:07:17PM 2 points [-]

He does not mean "lacking unnecessary details". For example the statements "Everyone just acts in his own interest" or "Everyone is really an altruist" are simple and lack unnecessary details, explain quite a lot, and are consistent with Occam's razor. But by Deutsch's criteria they are bad explanation because they are too easy to vary. For example, someone who believes in the self-interest theory could say, "John gave to charity because he would have felt guilty otherwise. So he really was selfish" .

We see that it is easy to change the theory that everyone is selfish to accomodate the case of someone who seems altruistic.

Or someone who believes in the altruist theory could say about John murdering Harry, "Well then, Harry must have been very unhappy."

The altruist theory and the selfishness theory are simple and explanatory in their own way, but too easy to vary. Similarly the idea that that sexism, feminism, capitalism, communism, parental coercion, environmental disregard, etc. cause unhappiness or mental illness or some other broad conclusion are equally meaningless. These explanations are bad because they can be varied to explain ANYTHING.

In contrast, theories that are difficult to vary go out on a limb. They are bold conjectures that explain a lot but even one small counterexample easily invalidates the whole thing. A good theory can not easily be changed to "take into account" the aberration. For example, Einstein's theory of gravitation is a good explanation because it explains a lot, it makes counterintuitive predictions, and even one repeatable counterexample invalidates the whole thing. It can't be easily changed to accommodate something else without invalidating everything else about it.

Theories that are hard to vary remain constant over time. They are more true and therefore more timeless. Invariable theories possess more verisimilitude ("truth-likeness" to use Popper's term).

Like the very best possible theory, truth also cannot be varied. It is completely timeless. It was, is, and always will be true, without any change. That is Deutsch's point.

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