Sunday, December 14, 2014

Book quotes: A Demon-Haunted World by Carl Sagan

Here is my collection of quotes and notes from Carl Sagan's wonderful "The Demon-Haunted World: Science as a Candle in the Dark", a book that should be compulsory reading in science classes everywhere.

 Carl Sagan

In hunter-gatherer, pre-agricultural times, human life expectancy was about 20 to 30 years. That's also what it was in Western Europe in Late and Medieval times. It didn't rise to 40 years until around the year 1870. It reached 50 in 1915, 60 in 1930, 70 in 1955, and is today approaching 80 (a little more for women, a little less for men).

The sword of science is double-edged. Its awesome power forces on all of us, including politicians, a new responsibility - more attention to the long-term consequences of technology, a global and transgenerational perspective ... Mistakes are becoming too expensive.

Pseudoscience speaks to powerful emotional needs that science often leaves unfulfilled. It caters to fantasies about personal powers we lack and long for (like those attributed to comic book heroes today, and earlier, to the gods).

Trotsky (1933): "Not only in peasant homes, but also in city skyscrapers, there lives alongside the twentieth century the thirteenth. A hundred million people use electricity and still believe in magic powers of signs and exorcisms...Movie stars go to mediums. Aviators who pilot miraculous mechanisms created by man's genius wear amulets on their sweaters."

Every time a scientific paper presents a bit of data, it's accompanied by an error bar - a quiet but insistent reminder that no knowledge is complete or perfect. It's a calibration of how much we trust what we think we know. If the error bars are small, the accuracy of our empirical knowledge is high; if the error bars are large, then so is the uncertainty in our knowledge. Except in pure mathematics nothing is known for certain (although much is certainly false).

The most each generation can hope for is to reduce the error bars a little, and to add to the body of data to which error bars apply. The error bar is a pervasive, visible self-assessment of the reliability of our knowledge.  You often see error bars in public opinion polls ('an uncertainty of plus or minus three percent', say). Imagine a society in which every speech in the Congressional Record, every television commercial, every sermon had an accompanying error bar or its equivalent.

Again, the reason science works so well is partly that built-in error correction machinery. There are no forbidden questions in science, no matters too sensitive or delicate to be probed, no sacred truths. The openness to new ideas, sifts the wheat from the chaff. It makes no difference how smart, august, or beloved you are. You must prove your case in the face of determined, expert criticism. Diversity and debate are valued. Opinions are encouraged to contend - substantively and in depth.

Don't waste neurons on what doesn't work.

Michael Faraday warned of the powerful temptation 'to seek for such evidence and appearances as are in favour of our desires, and to disregard those which oppose them...We receive as friendly that which agrees with [us], we resist with dislike that which opposes us; whereas the very reverse is required by every dictate of common sense"

...if we don't practice these tough habits of thought, we cannot hope to solve the truly serious problems that face us and we risk becoming a nation of suckers, a world of suckers, up for grabs by the next charlatan who saunters along.

The lust of marvellous blunts our critical faculties.

...everything hinges on the matter of evidence. ...The more important we want it to be true, the more careful we have to be. No witness's say-so is good enough. People makes mistakes. People play practical jokes. People stretch the truth for money or attention or fame. People occasionally misunderstand what they're seeing. People sometimes even see things that aren't there.

Keeping an open mind is a virtue -but, as the space engineer James Oberg once said, not so open that your brains fall out. Of course, we must be willing to change our minds when warranted by new evidence. But the evidence must be strong. Not all claims to knowledge have equal merit.

The question is not whether we like the conclusion that emerges out of a train of reasoning, but whether the conclusion follows from the premises or starting point and whether that premise is true. Among the tools:

- Wherever possible there must be independent confirmation of the 'facts'.
- Encourage substantive debate on the evidence by knowledgeable proponents of all points of view.
- Arguments from authority carry little weight - 'authorities' have made mistakes in the past. ...Perhaps a better way is to say that in science there are no authorities, only experts.
- Spin more than one hypothesis. If there's something to be explained, think of all the different ways in which it could be explained. Then think of tests by which you might systematically disprove each of the alternatives. What survives, the hypothesis that disproves Darwinian selection among 'multiple working hypothesis', has a much better chance of being the right answer than if you had simply run with the first idea that caught your fancy.
- Try not get overly attached to a hypothesis just because it's yours. It's only a way-station on the pursuit of knowledge. Ask yourself why you like the idea.
- Quantify. ...what is vague and qualitative is open to many explanations. Of course, there are truths to be sought in many qualitative issues we are obliged to confront, but finding them is more challenging.
- If there's a chain of argument, every link in the chain must work (including the premise) - not just most of them.
- Occam's Razor. This convenient rule-of-thumb urges us when faced with two hypothesis that explain the data equally well to choose the simpler.
- Always ask whether the hypothesis can be, at least in principle, falsified. Propositions that are untestable, unfalsifiable are not worth much. Consider the grand idea that our Universe and everything in it is just an elementary particle - an electron, say, in a much bigger Cosmos. But if we can never acquire information from outside our Universe, is not the idea incapable of disproof?

Control experiments are essential / Variables must be separated / often the experiment must be done 'double-blind. Any good baloney detection kit must also teach us what not to do:

- Ad hominen - Latin for 'to the man', attacking the arguer and not the argument.
- Argument from authority
- Argument from adverse consequences (e.g. the defendant must be found guilty; otherwise, it would be an encouragement for other men..)
- Appeal to ignorance - the claim that whatever has not been proved false must be true.
- Special pleading
- Begging the question/assuming the answer (e.g we must institute the death penalty to discourage violent crime, or the stock market fell yesterday because of a technical adjustment and profit-taking by investors.
- Observational selection ...or as the philosopher Francis Bacon described it, counting the hits and forgetting the misses.

Sagan writes: My favourite example is this story, told about the Italian physicist Enrico Fermi, newly arrived on American shores, enlisted in the Manhattan nuclear project, and brought face-to-face in the midst of World War Two with US flag officers:
So and so is a great general, he was told.
'What is the definition of a great general?' Fermi characteristically asked.
'I guess it's a general who's won many consecutive battles.'
'How many?'
After some back and forth, they settled on five.
'What fraction of American generals are great?'
After some more back and forth they settled on a few percent.
But imagine, Fermi rejoined, that there is no such thing as a great general, that all armies are equally matched, and that winning a battle is purely a matter of chance. Then the chance of winning one battle is one out of two, or 1/2; two battles 1/4, three 1/8, four 1/16, and five consecutive battles 1/32, which is about three per cent. You would expect a few percent of American generals to win five consecutive battles, purely by chance. Now, has any of them won ten consecutive battles?

- Statistics of small numbers (e.g. they say 1 in 5 people is Chinese. ...I know hundreds of people, and none of them is Chinese. Or I've thrown three sevens in a row. Tonight I can't lose.)
- Misunderstanding the nature of statistics (e.g. being surprised that half of the population are below average).
- Non sequiter - Latin for 'it doesn't follow' (e.g. our nation will prevail because God is great. Often results from failing to recognise the alternative possibilities.
- Post hoc, ergo procter hoc - Latin for 'it happened after, so it was caused by'. e.g. before women got the vote, there were no nuclear weapons.
- Excluded middle, or false dichotomy - considering only the two extremes in a continuum of intermediate possibilities. e.g. either you love your country or you hate it.
- Short-term v. long-term - a subset of the excluded middle. we can't afford to educate kids / feed malnourished children. We need to urgently deal with crime on the streets.
- Slippery slope - e.g. if we allow abortion in the first few weeks of pregnancy, it will be impossible to prevent the killing of a full-term infant.
- Confusion of correlation and causation (e.g. a survey shows that more college graduates are homosexual than those with a lesser education. Therefore, education makes people gay).
- Straw man - caricaturing a position to make it easier to attack.
- Weasel words e.g. calling wars 'police actions', 'armed incursions', 'protective reaction strikes', 'pacification'.

Knowing the existence of such logical and rhetorical fallacies rounds out our toolkit. Like all tools, the baloney detection kit can be misused, applied out of context, or even employed as a rote alternative to thinking. But applied judiciously, it can make all the difference in the world, not least in evaluating our own arguments before we present them to others.

Part of the success of the tobacco industry in purveying this brew of addictive poisons can be attributed to widespread unfamiliarity with the baloney detection kit, critical thinking and the scientific method. Gullibility kills.

One of the saddest lessons of history is this: if we've been bamboozled long enough, we tend to reject any evidence of the bamboozle. We're no longer interested in finding out the truth. The bamboozle has captured us. It's simply too painful to acknowledge , even to ourselves, that we've been taken.

Baloney, bamboozles, careless thinking, flimflam and wishes disguised as facts are not restricted to parlour magic and ambiguous advice on matters of the heart. Unfortunately, they ripple through mainstream political, social, religious and economic issues in every nation.

There are many better responses than making the child feel that asking deep questions constitutes a social blunder. If we have an idea of an answer, we can try to explain. Even an incomplete attempt constitutes a reassurance and encouragement. If we have no idea of the answer, we can take the child to the library. Or we might say: 'I don't know the answer. Maybe no one knows. Maybe when you grow up, you'll be the first person to find out.

There are naive questions, tedious questions, ill-phrased questions, questions put after inadequate self-criticism. But every question is a question to understand the world. There is no such thing as a dumb question.

Bright children are a national and world resource. They need to be cared for, cherished, and encouraged. We must also give them the essential tools to think with.

Ignorance feeds on ignorance. Science phobia is contagious.

Given our manifest human limitations, what is surprising is that we have been able to penetrate so far into the secrets of Nature.

'We also know how cruel the truth often is, and we wonder whether delusion is not the more consoling' - Henri Poincare (1854 - 1912)

We are rarely smart enough to set about on purpose making the discoveries that will drive the economy and safeguard our lives.

If we can't think for ourselves, if we're unwilling to question authority, then we're putty in the hands of those in power. But if citizens are educated and form their own opinions, then those in power work for us. In every country, we should be teaching our children the scientific method and the reasons for a Bill of Rights. With it comes a certain decency, humility and community spirit. In the demon-haunted world that we inhabit by virtue of being human, this may be all that stands between us and the enveloping darkness.



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