Informal Logic 101: How to Think and Argue Better, Part 7

Part 7: Causes and Comparisons

“Correlation does not equal causation.”  — many people, including me (‘cuz it makes me sound smart)

We’re baaaaaaack, and we have a lot of ground to cover, so let’s get started!

Cause-and-EffectClear thinking & reasoning require at least a basic understanding of causal relationships. Unfortunately, it’s also easy to make logical mistakes in this area. As you may have gathered from the header, our current group of fallacies primarily deals with causes (and effects), while the last one is about making comparisons to give rhetorical (if not logical) force to an argument. And, yes, we have a healthy dose of Latin to make it all sound properly intellectual. We will start with the three main types of “false cause” fallacy, the first being…

Post hoc, ergo propter hoc

This phrase translates to “after this, therefore because of this”. It refers to when one too quickly assumes that ‘A’ is the cause of ‘B’ just because ‘A’ occurred before ‘B’. Or, as Anthony Weston puts it in A Rulebook for Arguments, “assuming causation too readily on the basis of mere succession in time.” Yeah, that’s what I said.

Obviously, succession in time is, on its own, insufficient proof of cause & effect. Star Trek (the original series) debuted on Sept. 8, 1966, and I was born four days later. I also became a huge fan of the show and its successors. Was there any causal relation between the show’s debut and my birth? How about the show’s debut and my eventual affinity for it? Well, much as I like to think we were fated to be “together”, the answer to both questions is “No.”

Another example that is more common (and, yet, more controversial) would be the basic assumption of Darwinian evolutionists that organism ‘A’ must have evolved from similar organism ‘B’, because ‘A’ precedes ‘B’ in the fossil record. Both metaphysical naturalism and/or strong methodological naturalism precludes them from even entertaining the idea that similarity or “kinship” between the two organisms may be the result of them having a Designer in common. Such a Designer may have done as little as tweaking the genetic code of organism ‘A’ (or a common ancestor) to eventually produce organism ‘B’ OR s/he may have orchestrated the extinction of organism ‘A’ followed by the speciation by fiat of organism ‘B’. Regardless, one cannot assume a purely naturalistic, evolutionary linkage — i.e., a causal relationship — between the two based primarily on temporal succession.

Non causa pro causa

“Not the cause for the cause.” This one simply refers to the misidentification of an effect’s actual cause. For example, what would you think if I said, “The latest statistics for local juvenile delinquency just came out, and they show a more than 5% decrease in non-gun-related crime by teenagers over the past decade. I also just read an article observing that we have twice as many pizzerias in our city now as we did in 2003. So, it looks to me like more pizza is the answer to reducing crime among juveniles.”? Would you agree with my conclusion? I hope not. There may indeed be a correlation between available pizza hangouts and teenagers getting into trouble less often, but I sincerely doubt that it’s a substantial cause of the decrease. A much better study would need to be done to determine any real cause-and-effect.

This is connected to our next fallacy…

Oversimplified cause

Sometimes, we like to jump to conclusions, and sometimes that means latching onto a particular explanation for a thing. But, upon honest reflection, we know that the answer is often more complicated. There can be many factors involved that lead to a particular effect.

“The North fought the South in the American Civil War because of slavery.”

Well, as a former associate of mine was fond of saying, “It’s not that simple.” It’s true as far as it goes. Slavery was indeed a primary issue — maybe the primary issue — for moral, religious, socio-economic, and political reasons. One might even say that it became the lightning-rod, central issue for many that led to war. But, truth be told, there were several other reasons why people fought, and they often were interrelated. Some issues were more important for some people, and others for others. To imply that differences of opinion over slavery was the only cause of the Civil War would be an example of oversimplification.

These next two are special types of the false cause fallacy…

Sign saying, "Caution: Slippery Slope"Slippery slope

Sometimes referred to as the “domino fallacy”, this happens when someone claims that doing ‘X’ (either by an individual or a larger group) will set off a domino effect, with successive events inevitably leading to dire consequences. Now, not all slippery-slope arguments are fallacious, especially if one can demonstrate how using a particular way of reasoning for ‘X’ logically opens the door for the same reasoning being used to argue for ‘Y’, ‘Z’, and any number of other things. (The push for “same-sex marriage” falls under this.) The problem, however, is when assertions are made without sufficient reasons/evidence to back up the predicted chain reaction. For example:

“If we let kids play with toy guns, or even get used to seeing images of guns portrayed in a positive light, they will eventually start playing with real guns and start shooting each other, mugging and robbing innocent citizens, and generally grow up to be thugs and criminals.”

This, of course, is only part of a larger, anti-gun argument. But, history teaches us that this “logic” clearly does not bear out in real life.

Faulty analogy

An argument by analogy occurs when one observes or points out the similarities between two things and reasons that they probably have other characteristics in common, too. The first premise makes a claim about thing ‘A’. (First question: Is this claim true?) The second premise claims that thing ‘B’ is somehow like thing ‘A’, usually in more than one way. (Second question: Are the two examples relevantly similar?) Then, a conclusion is made. (Note: This may sound like a deductive syllogism, but analogies are actually a type of inductive reasoning.)

Analogies can be very helpful in thinking through ideas or illustrating a point to someone else. We use them all the time, so it’s important to think carefully about them. Sometimes, analogical reasoning is valid and works very well. Other times, though, not so much. If the proposed similarities are actually not significant to the issue (if they even exist) and, thus, the conclusion being drawn, then the analogy breaks down. Here’s a somewhat silly example:

“I hear Henry is one of those types that is really into the arts, especially when its tied to his cultural heritage, ‘cuz he’s kind of fanatical about that stuff. Come to think of it, Hitler and the Nazis were the same way. Henry’s probably just like Hitler!…”

Of course, appreciation of the arts and affection for one’s cultural heritage have no direct, let alone exclusive, connection to Nazi ideology or practices. The “similarities” are inconsequential and the argument’s conclusion is waaaaay off the mark.

The focus here is on not using bad or false analogies, which is usually done by overestimating the strength and/or relevance of the similarities. Another problem, though, comes from the other side — i.e., dismissing an argument by analogy simply because the analogy doesn’t go far enough, the similarities aren’t numerous or exact enough to satisfy. Of course, this is unfair, because no analogy can be “perfect”, else the two things being compared would be essentially identical and no analogy needed. Analogies are only meant to be taken so far. Also, remember that, since they are inductive rather than deductive, analogies can only be suggestive, not conclusive.

C-A-B interaction of kai proteinsAs Prof. Samples reminds us, “Good analogies compare things that have solid connections, directly relate to the conclusion, and pay careful attention to dissimilarities.” A great (though controversial) example of an argument by analogy is the “Watchmaker analogy” used in support of Intelligent Design Theory. William Paley’s argument for design in nature and, by extension, for God’s existence, can be boiled down to this:

“1) Watches display design.

2) Watches are the product of a watchmaker.

3) Organisms display design.

4) Therefore, organisms are the product of a Designer/Creator.”

Skeptics have long since pointed to the critical analysis of David Hume (1779) as a supposed debunking of Paley’s argument, concluding that living systems are not sufficiently similar to man-made mechanisms to warrant the analogy, or at least the likeness is not strong enough to justify the conclusion of the ID theorist. But recent developments in biochemistry have led some scientists and philosophers to rethink Paley’s design argument. Dr. Fuz Rana has reported on several amazing discoveries. Actual biomolecular motors provide “a strict analog to man-made machinery.” Even more intriguing and directly applicable to Paley’s argument are the mechanical molecular clocks inside cyanobacteria (photosynthetic blue-green alga) — i.e, real, honest-to-God (heh!), biochemical timekeeping devices (see illustration above). The Watchmaker analogy has been vindicated!

“This mechanism being observed… the inference we think is inevitable, that the watch must have had a maker.”  — William Paley (1802)

We got through five informal logical fallacies today? Whew! Good job!

Prof. Samples’ lesson for the day?

LESSON: “Exercise caution in analyzing causal relationships and conceptual comparisons.”


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