The Post Hoc Fallacy Fallacy

Great Debates
21

The cigarette studies were touted at proof long before they had sufficient real evidence that cigarette smoking did indeed cause cancer. Dozens of additional studies all showed the same correlation, even after removing other factors. But the mechanism of causation was not known, and still remains incompletely revealed. The evidence was sufficient to convince a lot of people, but it falls short of proof. The reason is that it is insufficient that the correlation exists, the mechanism of causation must be revealed. That takes a different level of examination than simple statistics.

Statistical analysis is a slippery devil. Cancer is caused by exposure to graduate students. You can prove it, statistically. Control populations in laboratory cancer studies have a higher incidence of cancer than do captured members of the same species. The lab animals are deliberately not exposed to carcinogens in the test. Yet they have a higher rate of cancers found in autopsy than are found in animals taken from the wild. One factor that laboratories have that wild places do not have is higher levels of population of graduate students.

The problem is that laboratories themselves are a factor. So too is the limited genetic diversity of lab animals. So, you don’t rely on the statistical data to prove anything, you use that data to indicate what you should study. If you really are worried about the graduate students, you higher illiterate migrants to care for your animals, and keep the grad students out of the building. If your results indicate a drop in cancer rates, you may be on to something. But probably, it won’t change. Not graduate students. Maybe fluorescent lights? Gary Larson cartoons?

If you base your entire proof on statistics, you have proven nothing but you own ability to assemble statistics. Post hoc ergo propter hoc is not true, even when the antecedent did cause the result. The contention is that ‘therefore’ the antecedent is causal. Simple correlation does not even examine the mechanism of causation.

Statistics are a good tool, for determining a direction for investigation. But there are other areas than science in which they are valuable. Insurance companies don’t care why male drivers between 16 and 19 are more likely to cause expensive damages with automobiles. They know it happens. They charge rates based on that knowledge. They are not wrong.

Red cars go faster than brown cars. It certainly is ridiculous to think that color affects the speed of an automobile. But the fact is that if you stand on the edge of the highway with a radar gun for a week you will find out that red cars go faster than brown cars. Why? So far, every thing I have read on the subject is speculation on psychology. But they do go faster, even so. Now, is it wrong to say that the car goes faster because it is red? Yes. Implying that I understand the mechanism of causation is incorrect. I know that they go faster. I don’t know why.

The error is in the implication of understanding cause.

Tris

“Criticism comes easier than craftsmanship.” ~ Zeuxis ~ (400 BC)

22

I think I was one of them… I don’t know if it was you I was replying to, but it was post-hoc-related, alright. We were talking about religion in government and to what extent we should have a separation of church and state.

23

More of a meta-debate, I think. And where do those belong?

I’ve been staying away from Great Debates because they don’t seem to go anywhere, but I looked at this one because someone I know loves to use post hoc ergo propter hoc to dismiss arguments he disagrees with…which is how people usually use it. So I’m delighted with the Post Hoc Fallacy fallacy; it’s something I’ll use to hit back with, even if I’m just using it to dismiss an argument I disagree with. He started it.:stuck_out_tongue:

24

Its probably the most irritating fallacy because it is so common, there is no good English translation of it and when you try to explain why one isn’t the cause of another they suddenly pretend that logic is too fancy for what everybody knows. Frankly ad hominems are less annoying.

25

Thanks, Dryga_yes. I check that thread and found that MEBuckner had mentioned Post Hoc:

I had written, “I find this argument quite logical, but it hasn’t worked in the real world. E.g., Nazi Germany specificially disavowed Christianity. Lenin and Stalin had no religion in their government. OTOH, the US, England, etc., who had a more-or-less Christian base, wound up with excellent civil liberties.” MEBuckner responded, "Post hoc, ergo propter hoc. There are also plenty of examples of Christian establishmentarianism leading to tyranny and cruelty–often of one set of Christians oppressing another; Christian societies have become more free and more enlightened as their governments have become more secular and as they have guaranteed religious liberty for all. http://boards.straightdope.com/sdmb/showthread.php?threadid=99723

**phartizan **, thanks for you kind words.

26

The predominant language of both Great Britain and the United States is English, and both countries have excellent records of civil liberties. Conversely, in the primary languages of both Nazi Germany and Soviet Russia the word America is spelled with a “k”, which everyone knows is one of the telltale signs of Evil Totalitarianism.

27

You’re stupid. They are not.

28

Sorry, the word “to” shouldn’t have been in the sentence. Triskadecamus summed up my view on the subject more elegantly than I could have. A good correlation does not pinpoint causation. Once the true fundamentals of the correlation have been discovered, there is no need to rely on the mere existence of the correlation for support.

In a debate, it might be nice if your opponent helped you discover the true nature of the correlation. But if he would rather use post hoc ergo propter hoc, then you must do the dirty work yourself.

29

Tris - what you say is all very true in theory. But the fact remains that unless you assume that there is some causation going on somewhere, you can’t extrapolate. Every time we extrapolate some statistics in an insurance pricing exercise, we are in effect assuming a causation - a causation that is not justified by an underlying mechanism.

Note that the causation needn’t be direct. And you’re right - we don’t necessarily care what the cause is. But in your red and brown car example we could argue a cause all right: that the kind of person who likes to drive fast is the kind of person who buys a red car. This is still a causal link. It isn’t coincidence that the red and brown cars have different speeds. This is the crucial point I think.

pan

30

kabbes, I don’t think you’ve disagreed with Tris at all. As he says, statistics are useful in determining where to look for causation (which I took to mean the same thing you’re driving at when you speak of extrapolation). Insurance companies are not in the business of extrapolation (although they certainly benefit from robust scientific studies), so, where a strong correlation can be shown (e.g. 16 - 19 y.o. drivers and accidents) they simply don’t need to establish specific causation.

Unfortunately, this type of approach, while sufficient for the estimation of probable risks and benefits, is inadequate as a basis for preventive or corrective actions. Thus, if we assert that there’s a probable psychological link between aggressive driving and chassis color preference, we’ve not committed any breaches of logic. But if we suggest that this information “proves” a prohibition against red paint on cars would be likely to reduce the incidence of speeding, we’ve run afoul of the post hoc ergo propter hoc fallacy.

31

There is, in my experience, a very low correlation between statistics and laughter.

However, there is a very direct causation between kabbes closing line above and the spewed coffee on my monitor.

[sub]…love this thread…[/sub]

32

No, no… not frank ad hominems! :stuck_out_tongue: :smiley:

I agree that a simple dismissal of causality is not sufficient, in my mind, to counter implied causality (insert relative Monty Python “argument” sketch here). post hoc counters should not be used, IMO, to decimate an argument. Though it should be up to the poster suggesting the causality to support it, it is very difficult to fully explain causal relationships when the other party is wont to disagree, and, frankly, the party who is disagreeing would have a ahrd time explaining why—exactly—they think one doesn’t follow from the other. Anyone interested in testing this with me, I have two fun examples.

33

Let’s have some fun, then. :slight_smile:

While we wait, though, I submit that a simple dismissal of causation is, in fact, entirely sufficient to refute an argument where a) broader inferences are drawn from the supposed causative link and b) no plausible mechanism is theorized to explain the causation. (“Plausible” in this case would mean a mechanism for which ample evidence exists in the form of established principles and observable phenomena.)

For example, if I were to assert that, based on the fact that all nations with high standards of living also have highly developed ground transportation infrastructures, road and rail systems are a necessary component of any transitioning third-world country, then my opponent could legitimately request that I show more than that basic correlation. My assertion could very well be quite valid, but until I demonstrate a mechanism I haven’t offered a strong argument in support, and my opponent need only focus on that lack.

34

So, xen, I was driving down the highway the other day when I noticed that as I passed a light (and other cars were passing other lights) they came on. Hence, there must be some mechanism whereby cars turn on streetlights.

35

post hoc.

heheheh

36

Xeno - I’d disagree. Insurance companies are in the business of extrapolation.

If there is no causation, then there is nothing to suggest that the observed correlation will occur again in the future.

The very fact that we do use data to price and reserve risks indicates that although we don’t know or care what the underlying causes are, we believe that the causes are there. We trust in those causes enough to assume that they will carry on causing the same claims in the same pattern as they have before.

That’s extrapolation. It is extrapolating the past to the future. Only if you believe that what happened before will happen again can you do this.

Without causation, all you have is coincidental order in the random patterns. You couldn’t do diddly with that.

pan

37

erislover, that’s an interesting thing. Did you stop to observe the phenomenon of lights turning on to see if they turned off after a set time? I don’t doubt that the lights came on as you describe, but I wonder what the precise mechanism is. Certainly, it could be that the street on which you drove has light actuating switches set to trip on the passage of vehicles. It’s one of many possibilities. I can suggest a few methods by which you could make a more certain determination…

Of course, since you haven’t proposed any particular light-avoidance/preventive/stimulative action, or based any social theory on your supposition regarding the lights, it really doesn’t matter whether I agree that the cars caused them to turn on. I trust that you observed the correlation, and I agree that there could be a causative link.

:wink:

38

kabbes: If all you mean is that insurance companies assume that strongly correlated phenomena will continue to exhibit correlation in similar circumstances, then I agree that they are in the business of extrapolation, and I withdraw my assertion to the contrary.

I continue to believe however that, while risk assessment doesn’t require one to identify causation, creating any theory regarding the significance of correlated phenomena does.

39

Okiedokie Xeno. We are in agreement. But do you know, for the life of me I can’t remember what my original point was?

I think it was merely in support of december’s observation that just because correlation doesn’t imply causation, one shouldn’t dismiss the correlation out of hand. Correlation strongly implies that there is some causative event at some level. In the context of a debate, this is worth further investigation.

pan