Compound Reasoning

Compound reasoning is reasoning in which the reasons given are best interpreted as supporting fundamentally different conclusions.  In other words, compound reasoning is reasoning that involves multiple rationales.  Here is a simple example of compound reasoning.

Example 1

I think Ricky drove home.  His car is gone.  That's not good.  That guy was blitzed.

Here the speaker's intention is clearly to argue both that Ricky had driven home and that this is not a good thing. These are best represented as separate conclusions. If you doubt this, you could experiment with an alternative reconstruction.  For example:

The obvious problem with a rationale like this is that the principle is unwieldy and difficult to grasp.  (Alternatively, you might try modifying the above rationale by keeping the conclusion the same, but using two reasons, as in the first rationale. The problem with that approach is that the two principles you generate will either make little sense, or they will connect to only one of the sentences in the conclusion).

Here's another example of compound reasoning:

Example 2

As millions of happy patients will attest, a regular visit to a chiropractor promotes physical health and well-being.  An experienced chiropractor can diagnose and correct skeletal misalignment that prevents neural pathways from functioning properly.  According to chiropractic medicine, blocked neural pathways caused by skeletal misalignment contribute to conditions as diverse as allergies, arthritis, depression and even cancer.

This example illustrates the importance of the distinction between argument and explanation. Notice first that both rationales have the same conclusion.  So, why do we need two rationales at all?  Why don't both chains simply connect to one conclusion?  The answer, or course, is that one chain is argumentative and the other is explanatory. The author first gives us evidence that chiropractic medicine promotes health and well-being.  Then, assuming that the evidence has established this conclusion as a fact, the author proceeds to explain just why (or how) chiropractic medicine brings this fact about.  Of course, this will be lost on anyone who does not know the difference between an argument and an explanation.  Moreover, such a person will be inclined to give this reasoning more credibility than it deserves. Notice that the only evidence given in support of the conclusion is that many patients say that chiropractic medicine works.  The rest of what was said simply assumed the conclusion as a fact and explained why it was so.  However, if we were to reject that assumption because we found the evidence unconvincing, then the explanation will be of little interest to us. 

Remember: Do not allow explanations  to convince you that a conclusion is true.  Explanations, by their very nature, simply assume that the conclusion is true.

Example 3

Reasoning that combines argument and explanation is so common that it deserves a name.  We'll call it exargative reasoning (short for explanatory-argumentative reasoning) Here is another example of exargative reasoning. 

I think its stupid that kids have to wear bike helmets.  When I was a kid, nobody had even heard of a bike helmet.  If somebody had shown up with one of those dorky looking things on his head we would have laughed it right off his head.  I guess people think that kids are safer with helmets on, but I sure don't.  What they don't realize is that kids who wear helmets just ride crazier and get hurt more often as a result.  I see these kids today riding down stairways and doing jumps off 20 foot ramps.  It's nuts.

You'll notice that the author of this reasoning produced an argument that a certain policy is flawed (mandatory bike helmets for kids) together with an explanation of the fact that the policy is in place. This is a very common exargative pattern, and it's not hard to understand why.  Suppose the author had only given us her argument against kids wearing bike helmets.  This is a pretty controversial position, since bike helmets are widely believed to keep kids from getting hurt.  If bike helmets really don't keep kids from getting hurt we would naturally want to know why kids are in fact required to wear them. The author senses this and offers us her own explanation, namely that people don't realize that the bike riding behavior of helmeted kids is more dangerous.

Pay particular attention to how R1 and R2 are reconstructed.  R1 of the explanation does not say "Helmets make kids who ride bikes safer."  That's because the author of this reasoning doesn't assert this. In fact, she clearly does not even believe this.  What she asserts is that this belief is widely held by others. The fact that this belief is widely held is what she thinks explains the existence of the bike helmet policy. Similar considerations apply to R2.  Whenever you are reconstructing reasoning you absolutely have to distinguish between what an author is asserting herself and what the author is asserting about the beliefs of others.

Let's look at one more example.

Example 4

Let me tell you Danielle, I had pretty bad acne just like you until I was about 16.  But I got rid of it by completely cutting chocolate out of my diet.  I know that's what it was because I quit eating it soon after my 16th birthday.  Here, look at this picture.  Pretty bad, huh?  Now look at this graduation picture when I was 17. The hottie right there on the left? That's me. So, my otherwise beautiful daughter, take it from someone whose been there: if you want to zap the zits, you got to chuck the chocolate.

This reasoning sounds very simplistic, but it has an interesting structure.  The author initially explains acne as the effect of eating chocolate.  This is followed by an argument in support of the claim that chocolate causes acne.  In other words, she produces an argument in support of the original explanation. This is what we call a causal argument.  In a causal argument an explanation occurs, not as a rational, but as a conclusion of the form "A causes B."  Again, it's not hard to understand why explanations and causal arguments would tend to go together. People often find explanations rather dubious.  In this case, we can imagine Danielle accepting both that her mom had acne as a teenager, and that her mom ate chocolate, but doubting that chocolate actually caused the acne.  The mother realizes this, and provides a certain amount of evidence for it.  (As you probably realize, it's pretty limited evidence.)

The third rationale above is an argument for the normative conclusion that Danielle should stop eating chocolate.  (The mother doesn't actually say this literally, but it is a reasonable interpretation.)  Now if you are paying attention you might wonder why there have to be two arguments here.  Why can't we just have a single argument that looks like this?

The answer is that we can, and this is actually a preferable interpretation.  The first reconstruction creates two arguments where there really is just one.  This is easy to do, but it is definitely a mistake.  By representing the reasoning as as containing two unrelated arguments, we create the impression that the reasoning is fragmented when it is actually quite unified.

Example 5

Leon been avoiding me. Maybe he thinks I'm pissed off at him.  That would make sense.  After all, he basically stole my girlfriend. He asked her out without even asking me if  I minded.  But, what's funny is that I don't even care anymore.

Let's consider two possible interpretations of this reasoning.

Interpretation 1

Interpretation 2

Both of these reconstructions make sense on their own, but a close reading reveals that the second interpretation is more accurate, even though the first is simpler and easier to understand. On the first interpretation the reasoning is entirely explanatory.  R1 is clearly intended to explain the conclusion, but it is expressly identified as an opinion. An explanatory opinion is also known as a hypothesis. Alex then goes on to support this hypothesis with the evidence that Leon behaved badly toward Alex. Hence, we are actually presented with both an explanation and an argument.

If the idea of an explanatory opinion is confusing to you it may be because you have come to think that an explanation must be factual.  That is too crude.  It is only the conclusion of an explanation that must be represented as a fact.  The reason may be presented as factual, but it may be completely hypothetical. If you say:  "I'll bet Isaac is late for class because he overslept," you have offered a hypothesis that explains why Isaac is late for class.  You are not presenting the statement "Isaac overslept" as a fact, but as an opinion that explains why he is late.