Carnival of the Africans #11

The 11th edition of the Carnival of the Africans is out over at The Skeptic Detective. My picks: Simon of Amaneunsis with some fact checking on pregnancy and sushi, George Claassen at Prometheus Unbound on religion in South African state schools, and Richard at The Botswana Skeptic on fortune tellers and the law...

We need a host for next month, so email me if you're interested...

Fun with fallacies: Poisoning the well

An unfortunate byproduct of philosophical training, other than the obvious of annoying everyone at the dinner table, is that I cry inwardly every time I see terms such as “fallacy” or “invalid” misused. On the theory that I shouldn’t complain about it if I’m not doing something about it, I figured I’d start an irregular series on critical thinking and logical fallacies. So, welcome to the inaugural edition of Fun with Fallacies…

First, some background. There are two different dimensions along which to evaluate arguments: one, the truth of premises and, two, the validity of argument structure. Premises (the content of arguments – e.g. “Scotland is in the Northern Hemisphere”, “All monkeys are purple”) are either true or false. Arguments (the logical structure linking premises – e.g. “If A then B, A therefore B”, “A and B, therefore C”) are either valid or invalid. And these two dimensions, importantly, are separate. In logic, saying a premise is invalid makes no sense: it is much like saying someone has scored a touchdown in soccer. Similarly, arguments cannot be true or false; they are only ever valid or invalid. As the perceptive reader no doubt noticed, my first example of a premise was true and the second was false and my first example of an argument was valid (if you like your Latin, this particular structure is known as modes ponens) and the second was invalid. Note that you can have an invalid argument with true premises and a true conclusion (“Elephants are mammals, Elvis Presley is dead, therefore homeopathy is bollocks”), that you can have a valid argument with false premises and a false conclusion (“All women are pregnant, Angela is a woman, therefore Angela is pregnant” "All women are pregnant, Michael is a woman, therefore Michael is pregnant") and so on. These dimensions are entirely independent of each other. When an argument is (1) valid AND (2) has all true premises, we say it is sound (and therefore one you should accept); otherwise, it is unsound.

But what exactly is validity? It’s quite simple really. A valid argument is one where the truth of the premises guarantees the truth of the conclusion. In other words, if the premises are true, it follows, by the laws of logic, that the conclusion must be true. (But not vice versa). If this is the case, we say the conclusion ‘follows’ from the premises or that the truth of the premises 'transmits' truth to the conclusion. So if “A” and “if A then B” are both true, then you are forced to conclude that “B” is true (this is modes ponens again). Or, in words, if Paris is the capitol of France (“A”), and Paris being the capitol of France entails that the French seat of government is in Paris (“if A then B”), then it follows that the French seat of government is in Paris (“B”).

Okay, so what’s a fallacy? It’s just an argument that is not valid – that is, it’s an argument where the conclusion does not follow from the premises. Notice, however, that the fact that some argument is a fallacy does not mean the premises are false, nor does it mean the conclusion is false. Indeed, saying an argument is fallacious (i.e. invalid) entails nothing whatsoever about the truth of the premises or the conclusion. (You can, after all, defend a true conclusion with an invalid argument). Conversely, just because an argument is valid does not mean the conclusion is true, nor does it mean the premises are true: it’s just that if the premises were true you would have to accept the conclusion. (So if it really were the case that all monkeys are purple and that I am a monkey, I would be forced to accept that I’m purple). The upshot is that a concern with validity and detecting fallacies is only one aspect of evaluating positions but, of course, it’s an important part.

That’s about enough background, I think, so on the our first actual example… Regular readers will recall that I recently took on a local (i.e. South African) homeopath, one Johan Prinsloo. In a section of his website that he’s now edited but which is still available on Google Cache as I first saw it, Prinsloo made the following argument (emphasis in original):

The one thing that always catches my attention is the fact that generally the skeptics of Homeopathy also tend to be anti-religion or at least skeptical of religion.

What’s going on here? Well, it’s a beautiful example of poisoning the well, which is a sub-type of the ad hominem fallacy (‘arguing to the man’). Ad hominem is pretty widely misunderstood; some people seem to think that any insult or negative assertion about an opponent makes an argument fallacious. This is not correct. In fact, ad hominem has the form: “Sarah believes that P, Sarah has negative quality X, therefore P is false”. Clearly, this argument is invalid: there is no premise linking having negative quality X and the truth or falsity of P. The important bit, though, is that a conclusion is being drawn about a claim from the purported negative quality, if this is not done no fallacy is being committed. I might say, for example, that: “Homeopathy is bollocks”, “homeopaths tend to be dumb”, “the law of infinitesimals is false” and so on. As long as I’m not drawing an inference from “homeopaths tend to be dumb”, all I’ve done is thrown around an insult (which may or may not be true), I have not committed a fallacy. (Remember, truth and falsity is independent of validity and invalidity!). It’s possible, in fact, to make the argument about Sarah valid (so it’s no longer a fallacy), despite the fact that it’s still about a negative quality. All I have to do is insert the missing premise: “Sarah believes that P, Sarah has negative quality X, everything people with negative quality X believe is false, therefore P is false”. Note that the conclusion now does follow from the premises and it’s thus no longer a fallacy, but at the cost of making the ridiculous missing (or ‘suppressed’) premise explicit.

In Prinsloo’s case it’s clear that he’s attempting to preempt criticism of homeopathy by (in his mind) tarnishing the reputation of the skeptics: he is, in other words, poisoning the well. He is implying that critics of homeopathy have a negative quality (being religious skeptics), and therefore their views on homeopathy can be dismissed. This argument is obviously fallacious as it stands: there is no premise linking being a religious skeptic to having false beliefs about homeopathy, and thus the conclusion does not follow from the stated premises. To make the argument valid, Prinsloo would have to say something like "everything a religious skeptic believes is false" or "everything religious skeptics say about homeopath is false" and once you see that, it becomes obvious why the premise was kept implicit: it's ridiculous on the face of it. As far as I am aware, there is not even correlational evidence between religious skepticism and having false beliefs (indeed the opposite might be true), let alone evidence that religious skeptics are invariably wrong.

Carnival of the Africans -- call for submissions

Angela Butterworth, The Skeptic Detective, will host the next edition of the Carnival of the Africans on the 28th. Please check out the guidelines, and then submit your posts to skepticdetective@gmail.com.

Also, if you'd like to host an edition, email me at ionian.enchatnment@gmail.com....

Lazy Linking

"The Dark Matter of the Human Brain"

• Carl Zimmer on how the neuron doctrine -- basically, that neurons do the computational heavy lifting in the brain -- might be wrong, or at least radically incomplete. Glial cells, it turns out, may be far more important than previously thought.
• "If astrocytes [a type of glial cell] really do process information, that would be a major addition to the brain’s computing power. After all, there are many more astrocytes in the brain than there are neurons. Perhaps, some scientists have speculated, astrocytes carry out their own computing. Instead of the digital code of voltage spikes that neurons use, astrocytes may act more like an analog network, encoding information in slowly rising and falling waves of calcium. In his new book, The Root of Thought, neuroscientist Andrew Koob suggests that conversations among astrocytes may be responsible for 'our creative and imaginative existence as human beings.'"

"Cracking the Spine of Libel"

• Olivia Judson over at the NY Times on the horrendous way in which Simon Singh has been treated. Good news: the US senate is putting pressure on the English parliament to change their libel laws. Hopefully freedom of speech will prevail. 

"The Greatest Show on Earth: The Evidence for Evolution"

• PZ's review of Dawkins' latest book.
• "The enemy of ignorance is education, and the creationists know that; it's why there is so much effort by the religious conservatives to destroy public education. These are books that provide an end-run around the current deficiencies in science education in this one area, and what they ought to do is help people question the wanna-be theocrats. If they lie about evolution, if they are so transparently wrong about this one subject, maybe more people will wake up to the anti-science agenda so many are peddling in this country."

"Can I Take Your Son to Church?"

• Religious people try to get children young... even if their parents are atheists. C.f. Dawkins' "Good and Bad Reasons for Believing": religious people were "told to believe [crazy claims] when they were young enough to believe anything."

"Publish Less, Perish More"

• "What if we did a little more thinking and a little less sharing? What if a publication was thoroughly peer reviewed? But there’s no time for this, right? Everyone is too busy, right? There’s the rub. We’d have the time to check our research if we stop shotgunning our whims at every conference with two legs and a skimpy dress. Suddenly, we’d see the ridiculous page limit requirements relax. We’d no longer have to fit complex talks into 12.225 minutes. Most importantly, we might start to understand what the hell other people are talking about. Fancy that, a presentation outside your narrow niche that you can follow?"

"The Courthouse Ring: Atticus Finch and the limits of Southern liberalism"

• Malcolm Gladwell's most recent piece. I can't say I like it very much, but here it is anyway.

Skeptics Circle #119

The 119th edition of the Skeptics Circle is out at Cubik's Rube. Posts to check out: The Skeptical Teacher's account of skeptrack at Dragon*Con, weird things on Kurzweil's bollocks live-forever stuff, Effort Sisyphus on how skeptics are (probably) immune to scams, and negative entropy on how foot detox machines are nonsense.

Technology Quarterly

The Economist released their latest Technology Quarterly a while back, here are my belated picks:

• Attack of the drones (on the continued development of unmanned aircraft for surveillance and combat).
• 3D TV (much to my surprise, it seems 3D television may be coming our way soon).
• Air powered batteries (a new type of battery that uses oxygen from the atmosphere to charge itself so it can be much smaller and apparently it'll be cheaper too).
• AI and CAPTCHA's (argues CAPTCHA's are safe from wannabe Skynets. For now). 
• A factory on your desk (from 3D printers to Matter Compilers. Maybe). 
• Biohacking (the rise of amateur tinkering with biological systems). 

Encephalon #75

Welcome to the 75th edition of Encephalon, your bi-monthly round-up of the best neuroscience and psychology posts from around the intertoobies...

First up in this edition is Vaughn over at Mind Hacks, with two fantastic titbits: amazing brain scans of 500-year-old mummies and a case-study of a patient who had a nail hammered into her head by some quack in an attempt to treat persistent headaches.

The massive literature on how human cognition is affected by non-rational, largely sub-conscious and often unacknowledged biases continues to grow. Two contributors submitted posts in this general area: Dave of Cognitive Daily and Dave of Neuronarrative. Our first Dave covers some recent work on how mood affects memory: apparently being in a bad mood when trying to memorize a list of words nullifies some kind of category cross-talk and thus improves recall. Weird. Our second Dave submitted two posts: the first (c'mon, parse that...) covers further work on how memories can be manipulated (this time courtesy of video), and the second is on how temperate influences emotion.

While neither Mo at Neurophilosophy nor Ed at Not Exactly Rocket Science actually submitted to the carnival, they produced a gem of a post apiece so I thought it appropriate to include them: Mo on the 'fiber optics' of the vertebrate retina and Ed on the dance of the disembodied gecko tail.

Daniel and Greg at Neuroanthropology do some public service blogging with a three part take down of a bad study of Rule 34 ("if it exists, there's porn on it"). Part 1: Sex, lies and IRB Tape, Part II: SurveyFail redax, and Part III: Nature/Nurture: Slash to the rescue...

So how about some neuroscience? Andrew and Scicurious to the rescue... The latter discusses behavioral tagging as a mechanism for long-term memory formation, and the former has a post on how adult fear memories can be erased (well, in rats).

Brain Blogger submitted two pieces: Jared Tanner calls for ethical debate before we create an artificial brain and Meghan Meyer discusses how physical and social pain may share neural architecture.

Finally, the usual trifecta of posts from Sharp Brains: cognitive enhancement via both neuropsychology and pharmacology, working memory training vs. medication treatment for children with ADHD, and a retooled understanding of 'use it or lose it'.

The next edition of the carnival, as far as I can see, has not been scheduled, so email Alvaro to volunteer!

Quote: Carl Sagan

I just finished reading Carl Sagan's skeptical classic, The Demon-Haunted World and I found a lot of quotable material. Here's just one, in the context of the European witch hunts:

If we’re absolutely sure that our beliefs are right, and those of others wrong; that we are motivated by good, and others by evil; that the king of the universe speaks to us, and not to adherents of very different faiths, that it is wicked to challenge conventional doctrines or to ask searching questions; that our main job is to believe and obey – then the witch mania will recur in its infinite variations down to the time of the last man.