Regarding your example of income disparity: I might rather be born into a system with very unequal incomes, if, as in America (in my personal and biased opinion), there is a reasonable chance of upping my income through persistence and pluck. I mean hey, that guy with all that money has to spend it somewhere-- perhaps he'll shop at my superstore!

But wait, what does wealth mean? In the case where everyone has the same income, where are they spending their money? Are they all buying the same things? Is this a totalitarian state? An economy without disparity is pretty disturbing to contemplate, because it means no one is making an effort to do better than other people, or else no one *can* do better. Money is not being concentrated or funnelled anywhere. Sounds like a pretty moribund economy.

If it's a situation where everyone always gets what they want and need, then wealth will have lost its conventional meaning, and no one will care whether one person is rich and another one isn't. What they will care about is the success of their God, their sports teams, and their children.

I guess what I'm saying is that there may be no interesting way to simplify interesting moral dilemmas without destroying the dilemma or rendering it irrelevant to natural dilemmas.

Yes the answer is obvious. The answer is that this question obviously does not yet have meaning. It's like an ink blot. Any meaning a person might think it has is completely inside his own mind. Is the inkblot a bunny? Is the inkblot a Grateful Dead concert? The right answer is not merely unknown, because there is no possible right answer.

A serious person-- one who take moral dilemmas seriously, anyway-- must learn more before proceeding.

The question is an inkblot because too many crucial variables have been left unspecified. For instance, in order for this to be an interesting moral dilemma I need to know that it is a situation that is physically possible, or else analogous to something that is possible. Otherwise, I can't know what other laws of physics or logic apply or don't apply, and therefore can't make an assessment. I need to know what my position is in this universe. I need to know why this power has been invested in me. I need to know the nature of the torture and who the person is who will be tortured. I need to consider such factors as what the torture may mean to other people who are aware of it (such as the people doing the torture). I need to know something about the costs and benefits involved. Will the person being tortured *know* they are being tortured? Or can it be arranged that they are born into the torture and consider it a normal part of their life. Will the person being tortured have *volunteered* to have been tortured? Will the dust motes have peppered the eyes of all those people anyway? Will the torture have happened anyway? Will choosing torture save other people from being tortured?

It would seem that torture is bad. On the other hand, just being alive is a form of torture. Each of us has a Sword of Damocles hanging over us. It's called mortality. Some people consider it torture when I keep telling them they haven't finished asking their question...

Your point would be so much stronger, Eliezer, if you were allowed to ignore the role of models in rationality. But in all cases an infinity of alternative models may also account for what you think you have proven rationally. In your terms, no one can revoke the law that any belief in "accurate beliefs" rests on a priori assertions about what can exist and what constitutes evidence. It rests on a priori structures in your brain, designed to notice some things and not others.

Rationality is heuristic. In the case of waiting for water to spontaneously freeze at room temperature, it may be a marvelous heuristic not to hold your breath, but that's a straw man. What I'm worried about as a post-modern skeptic is what ways of organizing the world you and I have systematically failed to consider in our rational analyses. Because many internally consistent constructions of the world may be incommensurable, and yet lead not only to different predictions, but incommensurable predictions.

When you write about rationality as a way to defeat self-certainty, I'm excited and grateful. That's also how I use it. I'm more nervous when you write as if rationality is a tool that inevitably to accurate beliefs.

I like the spirit of what you're saying, but I'm not convinced that you've made a rational argument for it. Also, I'm concerned that you might have started with the conclusion that a rational argument must flow forward and constructed an account to justify it. If so, in your terms, though not in mine, that would make your conclusion irrational.

I think it can be perfectly rational to think backwards from any conclusion you want to any explanation that fits. Rationality is among other things about being bound by the requirement of consistency in reasoning. It's about creating an account from the evidence. But it's also about evaluating evidence, and that part is where it gets problematic.

In an open and complex world like the one we live in every day, weighing evidence is largely a non-rational (para-rational? quasi-rational?) process. We are operating only with bounded rationality and collections of murky impressions. So, your idea of making a checklist and somehow discovering who the best candidate is is already doomed. There is no truly evidence-driven way of doing that, because evidence does not drive reasoning-- it's our BELIEFS about evidence that drive reasoning. Our beliefs are mostly not a product of a rational process.

A logical explanation is one that follows from premises to conclusions without violating any rule of logic. Additionally, all logical explanations of real world situations involves a claim that the logical model we put forward corresponds usefully to the state of the real world. What we called a "cat" in our reasoning corresponded to that furry thing we understand as a cat, etc. If I can think backwards from a conclusion without finding an absurd premise, then I have a logical explanation. (It may be wrong, of course.)

To attack my self-consistent, logical account of a situation that suggests that X is TRUE, based solely on the fact that I was looking for evidence that X is true, is equivalent to an ad hominem fallacy. I think you can certainly suspect that my argument is weak, and it probably is, but you can't credibly attack my sound argument simply because you don't like me, or you don't like my method of arriving at my sound argument. A lot of science would have to be thrown out if a scientist wasn't allowed to search for evidence to support something he hoped would be true. Also, as you know, many theorems have been proven using backward reasoning.

If you want to attack the argument, you can attack it rationally by offering counter-evidence, or an alternative reasoning that is more consistent with more reliable facts. Furthermore, our entire legal system is built on the idea that two opposing sides in a dispute, marshaling the best stories they can marshal, will provide judges and juries with a good basis on which to decide the dispute.

Instead of calling it irrational, I would say that it's a generally self-deceptive practice to start from a conclusion and work backward. I don't trust that process, but I couldn't disqualify an argument solely on those grounds.

Instead of prescribing forward reasoning only, I would prescribe self-critical thinking and de-biasing strategies.

(BTW, one of the reasons I don't vote is that I am confident that I cannot, under any circumstances, EVER, have sufficient and reliable information about the candidates to allow me to make a good decision. So, I believe all voting decisions people actually make are irrational.)

Um, guys, there are an infinite number of possible hypotheses. Any evidence that corroborates one theory also corroborates (or fails to refute) an infinite number of alternative specifiable accounts of the world.

What evidence does is allow us to say "Whatever the truth is, it must coexist in the same universe with the true nature of this evidence I have accepted. Theory X and its infinite number of variants seems to be ruled out by this evidence (although I may have misinterpreted the theory or the nature of the evidence), whereas Theory Y and its infinite number of variants seems not yet to be ruled out."

Yeah, I realize this is a complicated way to phrase it. The reason I like to phrase it this way is to point out that Einstein did not have merely 29 "bits" of evidence, he had VAST evidence, based on an entire lifetime of neuron-level programming, that automatically focused his mind on a productive way of thinking about the universe. He was imagining and eliminating vast swaths of potential theories of the universe, as are we all, from his earliest days in the womb. This is hardly surprising, considering that humans are the result of an evolutionary process that systematically killed the creatures who couldn't map the universe sufficiently well.

We can never know if we are getting to the right hypothesis. What we can say is that we have arrived at a hypothesis that is isomorphic with the truth, as we understand that hypothesis, over the span of evidence we think we have and think we understand. Always the next bit of evidence we discover may turn what we think we knew upside down. All knowledge is defeasible.

Hi Eliezer,

I like the word entanglement, because it's a messy concept. Reality, whatever else it might be, is messy. That's why statements like the preceding sentence can't ever be completely true. The messiness makes it hard to talk about anything real in any absolutely definitive sort of way.

I can be definitive about artificial constructs in an artificial world, yes. Hence, mathematics. But when you or I try to capture the real world with that comforting clarity, we are doomed. Well, mostly doomed. 85.27% doomed, plus or minus an unknown set of unknowns.

That's the problem I have with your otherwise (as usual) thought provoking post: YES, our perceptions are entangled with the state of the world and that often influences our beliefs which then may entangle our utterances and therefore eventually entangle other people's beliefs. BUT what is the nature of that entanglement? You can't know for sure. What specifically are the beliefs that you intend to refer to? You can't know for sure.

The factor I expected to see in your essay, but did not, is *interpretation based on mental models*. There are many models I might have in my mind that could influence what counts as evidence.

You wrote: "For an event to be evidence about a target of inquiry, it has to happen differently in a way that's entangled with the different possible states of the target."

If we put the missing material about interpretation in there this might read:

"For me to consider an event to be evidence about a target of inquiry, I must first possess or construct a model of that event and that target and also a model of the world that contains and relates the event and target with each other. Then, for the event to be evidence CORROBORATING a particular theory about the target, I must imagine plausible alternative events that would that would CONTRADICT that theory."

Unfortunately, our models can be wrong, and *are* often wrong in interesting ways. So, we can satisfy your version of the statement, or my version, and still be counting as evidence things that may be no evidence at all. Example: "I was about to go for a car ride and a black cat crossed my path, which I interpret as a portent of evil, so I went back into my house. The black cat was evidence of evil in that particular situation because a black cat crossing my path is a rare event; it is possible for the cat not to have crossed my path; and in my culture, which is the collective product of successful experience staying alive and procreating, it is considered a portent of evil for a black cat to cross one's path. Had a black cat not crossed my path, I would consider that evidence (weak evidence) that I was not about to experience misfortune."

"Evolution does not operate on species. It operates on individuals. Genes that are statistically bad for individuals drop out of the gene pool no matter what they do for the species."

Imagine a gene that caused 9/10 of the humans who have it to be twice as fertility and attractiveness as the population that did not have it, while 1/10 of the humans who have it can't reproduce at all. This would be a gene that would serve the species (i.e. the portion of the species that had it), even though it would harm some individuals. Notice that the inability of the 10% to procreate would not harm the prospects of such a gene for the species as a whole. Soon, the whole of the species would have this gene.

Isn't there some theorizing that suggests that homosexuality may be an example of something like this? Perhaps the phenomenon of homosexuality is linked to some wonderful benefit that increases the viability of heterosexuals. Otherwise, wouldn't homosexuals have been "selected out" long ago?

I'm pleased to say that, through a great deal of study and practice, I *have* learned how to unlearn things that I know. This is called skepticism. A key to it is the ability to imagine plausible alternatives to whatever is believed. Descartes is famous for developing this idea, although he was constrained by his society from completely embracing it. Pyrrho and Sextus Empiricus developed this idea, but their community was persecuted and destroyed by the Christians, too.

Skepticism is not opposed to rationality, but neither does it accept that a rationally derived solution to a problem is *necessarily* the best solution (unless you define rationality as whatever leads to the best solution, in which case you have to abandon the notion of a rational methodology).

My wife is an ongoing experiment and example for me, because she seems to live her life almost entirely without rationality and critical thinking as I recognize it. She lives instead by pattern matching and by the process of comparing real and anticipated feelings. You feel superior to her. Well, she feels superior to you. Is there a non-biased process that can decide who is right? Sure there is: mutation and natural selection. My wife is the product of billions of years of evolution, as are you. So, it seems to be a tie...

I like being "smart" and "analytical". It's my kind of game. I find symbolic logic fascinating. I write software using my logical mind. I enjoyed reading your wonderful tutorial on Bayesian reasoning, though I already knew the material, having read the Cartoon Guide to Statistics and the works of Tversky and Kahneman, years ago. But not since 1920 or so has it been possible to make a fully rational case for living a fully rational life. To do that you have to base your reasoning on premises, and that leads to the infinite regress problem. You have to map your premises to reality, but you don't have direct access to reality.

I'm not attacking rationality. I love it. But why be biased in favor of it? Why not just do what works for you and leave it at that?

Curiously Eliezer, I feel like applauding. Good post.

Something seems out of kilter about this, Eliezer.

When I was 13, I thought I had a proof in principle that there must be a minimum possible distance-- because to move is to move a finite distance, but no sum of infitesimal distances can compose a finite distance. I shared my idea with a professional physicist, who dismissed my idea using an appeal to authority. I don't care how fabulous the authority was, nor how ignorant I may have been, it was a terrible thing to for him to do that. It killed my enthusiasm for questioning physics, or math, at the time.

Reasoning, even mathematical reasoning, is not about just about right and wrong. It's also about how we model the world and apply our models to it. See Imre Lakatos's wonderful Proofs and Refutations for a look at how proofs are not just proofs, they are assertions about what's worth talking about and what we mean by our words.

And reasoning is also about honing our skills. We must develop the guts to recognize when we are wrong, but also the guts not worry so much about being wrong that we give up before we learn very much.

I once discovered a way to trisect an angle with a compass and straight edge. This has been proven to be impossible, apparently, but I did it. Later I discovered that I used an operation that wasn't "allowed" (an approximation maneuver), even though I performed the maneuver with only a compass and straight edge. To me, the proof that it can't be done is obviously incorrect, by any practical standard. Show me an angle and I can trisect it to an arbitrarily high degree of accuracy with my mechanical procedure. I challenge the "rules" set out by whomever thinks he's the know-all on what can be done with a compass and straight edge.

I hope other 13 year-olds don't read your essay and decide that the rational attitude is never to try to reinvent or challenge the Ancient Ones.