Wednesday, April 17, 2013

Critical Thinking: Particular Causal Reasoning and Arguments from Ignorance

In the previous section we looked at general causal reasoning.  Now we're going kick it up a notch with particular causal reasoning.  Essentially, particular causal reasoning is when we apply causal reasoning to explain a particular effect in terms of a particular (or sometimes general) cause.  For example, I got bronchitis because of the fire down the street.  Contrast this with a general causal claim which might be something like "some people get lung infections from large fires."  

Notice that my particular causal reasoning implicitly relies on a general causal claim.  That is, it is an instance of the general claim.  Bronchitis is an instance of the more general category "lung infections" and the housefire-down-the-street is an instance of the more general category "large fires."  This fact will be important in our evaluation.

The Argument Structure of Particular Causal Reasoning
Recall that general causal reasoning has the structure "X causes Y," where X is all or most objects/events called X and Y is all or most objects/events called Y.  For example, if I say "food motivates dogs to perform tricks" we'd represent this argument as "X causes Y," where X=different types of food and Y=dogs performing tricks.

We can make a particular causal claim too.  I might say "pup-eroni motivates Ottis to sit."  We can represent the particular claim as "this x causes this y," where x=a type of food and y=a particular dog.  (Notice that in the general claim we use uppercase variables and in the particular claim we use lower case.)

So, why does all this alphabet soup matter?  Well, it's not too important but it illustrates that particular causal reasoning depends on more general causal reasoning.  In other words, for every particular causal claim there will be a more general claim upon which it depends.  Also, that the variables in particular claims are instances of more general categories.

Lets take a quick step back:  We know from our general critical thinking that the strength of a conclusion partly relies on the truth of a premise/premises (i.e., premise acceptability).   Consequentially, if we can show that that premise is weak, then the plausibility of the conclusion will be negatively affected.

As applied to particular causal claims, we should recognize that a particular causal claim has as a supporting premise a more general causal claim.  So, if we can show that the general causal claim is weak or strong (using the skills we acquired in the section on general causal reasoning) then this will impact the relative strength of the particular causal claim in the conclusion.

There are a few other ways to evaluate a particular causal claim.  Lets make the argument structure explicit first:

Argument Structure for a Particular Causal Argument
P1:  X causes Y.  (This is the general claim)
P2:  Appealing to the general causal principle in P1 is the best explanation of y.  (y=the particular effect)
C:   Therefore, this x caused this y.

So, we've already said that one aspect of our evaluation will involve evaluating the general claim upon which the particular claim relies.  The second will be regarding (P2):  Is P1 the best explanation of y? (y=the particular effect); that is, is y best explained in terms of the general claim in P1?  Or might there be better explanations?  Here we might appeal to other causal explanations for y.

This is How We Do It....(Note: I've added a few steps of analysis not included in your textbook)
We can illustrate how to evaluate a particular causal claim with an example:  Suppose someone makes the argument after winning at the casino that they won because they were wearing their lucky sweater.  (I've actually heard this).   We might say that the particular claim is an instance of the more general claim that certain objects can bring good luck.  Lets formalize the structure of the argument:

P1  Some objects can bring good luck. (Some Xs cause Y.)
P2  The principle P1 (i.e., some object bring good luck) is the best explanation of why I won at roulette.
C    Therefore, I won at roulette because I was wearing my lucky sweater.

Step 1
How might we evaluate this claim?  First a quick note:  the general claim of which the particular claim is an instance won't always be stated.  Often it will be up to the reader to infer it.  So, lets call that step 1.  In this case, the general causal principle we can infer from the conclusion is the some objects can bring about good luck in gambling (or just generally).

The general causal principle we infer (when not explicitly stated) will require a little bit of subjective judgment on our part to determine scope.  So, as I've indicated, in this example we might say that the general principle is that some objects bring good luck across all activities, or maybe they only bring good luck in gambling.  Here we should apply the principles of charity and reasonableness to avoid constructing strawmen.

Step 2
Decide whether the general causal claim is sound.  That is, apply the evaluative principles we learned in the previous section.  I won't repeat them here but, in this case we'd look at P1 and decide whether it is a good causal principle that some objects can bring about good luck.  We'd also consider questions about representativeness of the sample depending on what information is available to us.

Step 3a
Decide whether the principle in P1 is the best explanation of the effect (y).  Here we ask whether the fact that I had with me a particular "lucky" object (i.e., wore a particular sweater) is the best causal explanation of my good luck at the roulette table.  In other words, if we accept P1 as true--that some objects cause good luck--is the particular effect y (i.e., this instance of winning at roulette) best explained in terms of the implied general causal principle (that some objects bring about good luck)?

We can think of this type of evaluation in terms of comparing competing explanations.  We might ask, are there other plausible explanations for why I won at the roulette table?  If so, are they more likely than the one suggested?  If the competing explanations are more plausible than the one that's implied, this will have consequences on the plausibility of the conclusion.

In this case we might suggest that there is a more plausible general principle for why I won.  Statistically, someone (who places a bet) eventually will win at the roulette table and I just happened to be there at the right time and place.  If I had kept playing, regression toward the mean would have taken over and we'd have seen that my performance with the lucky sweater was no better than the general statistical odds of the game.

Step 3b
Related to the question of whether the general causal principle is the best explanation of the particular event we can ask an "identity" question.  That is, we can ask whether y really is an instance of Y and whether x really is an instance of X.   This step will be very similar to what we do when we evaluate generalizations.  

Lets quickly summarize how we'd go about evaluating a particular causal claim.  (1) The particular claim relies on a more general causal claim, so if the general claim isn't explicitly stated, you should try to infer what it is.  (2)  Decide whether the general causal claim is plausible (using the criteria from the section on general causal reasoning). (3a)  Decide whether the general causal claim (if assumed true) is the best explanation of the particular causal claim.  (3b)  Decide whether the particular cause and effect are indeed instances of the general categories of cause and effect in the general causal claim.


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