A little logic is a dangerous thing

Some famous and lovely lines from Alexander Pope’s “An Essay on Criticism” observe:

A little learning is a dangerous thing;

Drink deep, or taste not the Pierian spring.

There shallow draughts intoxicate the brain,

And drinking largely sobers us again.

Think of the person who has read one book on a subject and suddenly thinks he knows everything.  Or the beginning student of philosophy whose superficial encounter with skeptical arguments leads him to deny that we can know anything.  A deeper inquiry, if only it were pursued, would in each case yield a more balanced judgement.

Similar delusions of competence often afflict those who have studied a little logic.  Elsewhere I’ve discussed the phony rigor often associated with the application of formal methods.  Here, however, what I have in mind is the abuse of a more elementary part of logic – the study of fallacies (that is to say, of common errors in reasoning).

The principle of charity

Beginning students of logic, when they first learn the fallacies, often start thinking they can see them everywhere – or more precisely, everywhere in the arguments of people whose opinions on politics or religion they already disagree with, though not so much in the arguments of people on their own side.  (What are the odds?)  A good teacher will inform them that knowledge of the fallacies must be applied in conjunction with what is called the “principle of charity.”  This principle tells us that, when an argument that could be read as committing a fallacy could also be plausibly interpreted instead in a different way, we should presume that the latter interpretation is the correct one.

The point of this principle is not merely, or even primarily, to be nice.  The point is rather that the study of logic is ultimately about pursuing truth, not about winning a debate.  If we dismiss some argument too quickly because we haven’t considered a more charitable interpretation, then we might miss out on learning some important truth – perhaps a truth that we are reluctant to learn, precisely because it comes from someone we dislike. 

But it’s not just a failure to apply the principle of charity that can lead someone wrongly to accuse another of committing a fallacy.  Sometimes people just don’t correctly understand the nature of some particular fallacy. 

Ad hominem?

Let’s consider some common examples, beginning with the ad hominem fallacy.  What matters when evaluating an argument is whether its premises are true, and whether the conclusion really follows from the premises, either with deductive validity or at least with significant probability.  And that’s all that matters, logically speaking.  The character of the person giving the argument is entirely irrelevant to that.  Ad hominem fallacies are fallacies that neglect this fact – that pretend that by attacking a person in some way, you’ve thereby cast doubt on the argument the person has given or the truth of some claim he has made.

There are different ways this might go.  The crudest way is the abusive ad hominem, wherein, instead of addressing the merits of some argument the person has given, you simply call him names – “racist,” “fascist,” “commie,” or whatever – and pretend that sticking such a label on him casts doubt on what he said.  Another common variation on the ad hominem fallacy is the circumstantial ad hominem or appeal to motive, wherein one attributes a suspect motive to the person and pretends that doing so casts doubt on what the person says.  Of course, it does not.  A good argument remains a good argument, however bad the motives (or alleged motives) of the person giving it, and a bad argument remains a bad argument however good the motives of the person giving it.

It is crucial to emphasize, though, that calling someone a name, attributing bad motives to him, or in some other way attacking a person or his character is not in itself a fallacy.  It amounts to a fallacy only when what is at issue, specifically, is the merits of some claim he made or some argument he gave, and instead of addressing that, you change the subject and attack the person.

But of course, there are other contexts where the subject is the person or his character, rather than some argument he gave.  For example, if a jury is trying to determine whether a person’s eyewitness testimony is reliable, a lawyer is not committing an ad hominem fallacy if he notes that the witness has been caught in lies in the past, or is known to harbor a personal grudge against the person he’s testifying against.  Or, when you are deciding whether to believe a used car salesman, you are not guilty of an ad hominem fallacy when considering that his motive to sell you a car might bias the advice he gives you.  Again, in cases like these, what is at issue is not some argument the person gave, which might be considered entirely apart from him.  What is at issue is the credibility of the person himself. 

Or suppose you call someone a “jerk” precisely because he is acting like a jerk.  There is no fallacy in that.  Indeed, there is no fallacy even if he is not acting like a jerk, but you’re just in a bad mood.  Name-calling may be justified in the one case and unjustified in the other, but it is not a fallacy if the context isn’t one where the cogency of some argument he gave is what at issue, and you’re distracting attention from that.

People are especially prone to make the mistake of confusing attacks on a person with the ad hominem fallacy when the context is a debate or public exchange of some other kind – where, of course, one or both sides may be making arguments.  Suppose Person A and Person B are engaged in some public dispute (on a blog, on Twitter, or wherever).  Suppose Person A addresses the arguments of Person B, but Person B refuses to respond in kind, resorting instead to ad hominem attacks, or mockery, or changing the subject.  Suppose that Person A, appalled by this behavior, calls attention to Person B’s personal failings – characterizing Person B as intellectually dishonest, or as a sophist, or as a buffoon, or the like.  And suppose that Person B then objects to this and accuses Person A of committing an ad hominem fallacy.

Is Person A guilty of such a fallacy?  Of course not.  He has not attacked Person B as a way of avoiding addressing Person B’s claims or arguments.  On the contrary, he has addressed those claims and arguments.  His negative estimation of Person B’s character is a separate point, and a correct one.  Person B – whether out of clueless befuddlement or cynical calculation – makes of the false accusation that Person A is guilty of an ad hominem fallacy a smokescreen to hide the fact that it is really Person B himself who is guilty of this.

In the case I just described, a person is accused of committing an ad hominem fallacy when he is not in fact doing so.  But it can also happen that a person pretends (or maybe even sincerely believes) that he is not committing an ad hominem fallacy when he is fact doing so.  To change my example a bit, suppose Person A and Person B are engaged in some public dispute.  Suppose Person B never addresses Person A’s arguments, but simply and repeatedly flings terms of abuse, questions his motives, and so on, with the aim of undermining Person A’s credibility with his readers.  Suppose Person A accuses Person B of ad hominem fallacies, and Person B responds: “I’ve committed no such fallacy!  After all, using such terms of abuse is not by itself fallacious.  It’s only a fallacy when addressing an argument, and I haven’t been addressing your arguments.  I’m just telling people what a horrible person you are.”

Is Person B thus innocent of an ad hominem fallacy in this case?  Not at all.  He may not have committed this fallacy in a direct way, but he has still done so indirectly.  True, he has avoided addressing any specific argument Person A has given.  Hence he has not in that way committed an ad hominem fallacy.  At the same time, though, he has, through ad hominem abuse, tried to poison his readers’ minds against taking seriously any argument that Person A might happen to give.  Hence he has deployed a fallaciously ad hominem tactic in a general way.

The bottom line is this.  Is a speaker resorting to ad hominem abuse as a way of trying to avoid having to address some claim or argument another person has given?  If so, he is guilty of an ad hominem fallacy.  If not, then he is not guilty of such a fallacy (whether or not his abusive language is unjustifiable for some other reason – that’s a separate question).

Appeal to emotion?

An appeal to emotion fallacy is committed when, instead of trying to convince one’s listener of a certain conclusion by offering reasons that provide actual logical support for that conclusion, one plays on the listener’s emotions.  The strength of the emotional reaction makes the conclusion seem well-supported, when in fact the premises do not provide strong grounds for believing it.

But here it is important to emphasize that the presence of an emotional reaction does not by itself make an argument fallacious, not even if the speaker foresees such a reaction and indeed even if he intends it.  To take an artificial example in order to illustrate the point, suppose some follower of Socrates, having just heard the fatal verdict, wants desperately to believe that his hero Socrates will somehow never die.  You hope to bring him back to reality, and present him with the following argument:

All men are mortal

Socrates is a man

Therefore, Socrates is mortal

He contemplates this reasoning, sighs heavily and resigns himself to the cold, hard truth.  The argument raises profound emotions in him, as you knew it would.  But have you committed a fallacy of appeal to emotion?  Obviously not.  The argument is no less sound than it would be if someone with no emotional reaction at all had heard it.

Still, you might think, the reason there is no fallacy here is that the emotions in question are not such as to incline the person to want to believe the conclusion.  Quite the opposite.  But suppose the emotions in question were of that sort.  For example, suppose one of Socrates’ enemies feared that the hemlock would not kill him, and worried that perhaps Socrates was immortal and could never be gotten rid of.  Suppose you present him with the same argument just given.  He is reassured.  But have you now, in this case, committed a fallacy of appeal to emotion?

No.  Here too, the argument remains just as sound as it would be if some unemotional person who couldn’t care one way or the other about Socrates had heard it.  But what if you not only know that the person will be pleased by the conclusion, but intend for him to be pleased by it?  What if you hope that his positive emotional response to the argument will make him more likely to accept it?  Wouldn’t that make it a fallacious appeal to emotion?

No, it would not.  For the bottom line is that the premises are clearly true and the conclusion clearly follows validly from them.  The presence or absence of an emotional reaction, of whatever kind, does not change that in the least.  Hence there is no fallacy of appeal to emotion.  Such a fallacy is committed only when there is some logical gap in the support the premises supply the conclusion, which the emotional reaction is meant to fill.  But there is no such gap – and thus no fallacy.

Indeed, an emotional reaction can in some cases get a person to be more rational, not less.  In the second example, the person’s fear that Socrates might be immortal is unreasonable.  He’s letting his fear of Socrates’ influence within Athens get the better of him, and lead him to paranoid delusions.  The argument you give him, precisely because it is pleasing to him, draws his attention away from these paranoid feelings and back to reality.

Again, the example is admittedly artificial.  But there are many topics that do realistically carry heavy emotional baggage, yet where this does not entail that arguments having to do with them must be guilty of the fallacy of appeal to emotion.  Matters of life and death – war, abortion, capital punishment, and the like – are like that.  No matter what conclusions you draw and what premises you appeal to, they are bound to generate emotional reactions of some kind in your listener.  But that does not entail that you are guilty of a fallacy of appeal to emotion.

The bottom line is this.  Are the premises of the argument true?  Do they in fact provide logical support for the conclusion (whether deductive validity or inductive strength)?  Then the argument is not guilty of a fallacy of appeal to emotion, whether or not it also happens to generate an emotional reaction in the listener, and whatever that reaction happens to be.

Slippery slope?

A third fallacy that is widely misunderstood is the slippery slope fallacy.  Someone commits this fallacy when he claims that a certain view or policy will lead to disastrous consequences, but without offering adequate support for this judgement.  It is an instance of the more general error of jumping to conclusions or inferring well beyond what the evidence appealed to would support.

For example, suppose someone criticized a proposed small tax hike by claiming that it would inevitably lead to a radically egalitarian redistribution of wealth.  It is hard to imagine how this would fail to count as a slippery slope fallacy.  Is there a logical connection between raising taxes slightly and radically equalizing shares of wealth by way of redistribution?  No, and it is not hard to formulate principles that would both allow for some taxation while at the same time ruling out radically redistributive taxation.  Is there nevertheless some strong causal connection between raising taxes slightly and radically redistributing wealth?  Obviously not, since there have as a matter of historical fact been many cases where taxes were raised, but were never followed by a radically egalitarian redistribution of wealth.

Notice that the problem here, though, is not that the argument claims that bad consequences would follow.  The problem is that the argument did not back up this claim.  This is often overlooked by people who accuse others of the slippery slope fallacy.  They seem to think that any claim that bad consequences will follow from a certain view or policy amounts to a slippery slope fallacy.

In fact, there is no fallacy as long as someone explains exactly how the bad consequences are supposed to follow.  If you can show that A logically entails Z, or that it does so when conjoined with some other clearly true assumptions, then you have not committed a slippery slope fallacy.  Or if you can identify some specific causal mechanism by which A will lead to Z, then you have not committed a slippery slope fallacy.  You commit such a fallacy only when you jump from A to Z without filling in the gap between them.

What if you are wrong about the claim that A logically entails Z, or wrong about the causal mechanism you claim links them?  You are still not guilty of a slippery slope fallacy.  True, you are mistaken, and perhaps guilty of some other logical error.  But you haven’t committed a slippery slope fallacy, specifically, if you at least proposed some specific means by which A would lead to Z.

There are other fallacies too that are often misunderstood, but that suffices to make the point.  Knowledge of the fallacies is essential to reasoning well, but it is of limited value if it is merely superficial knowledge, and may in that case even impede careful reasoning.  It can lead to seeing fallacies where they do not exist, and thus lead away from truth rather than toward it.  And if one’s knowledge of fallacies is deployed merely as a further rhetorical means of trying to make an opponent look bad, it constitutes sophistry rather than remedying sophistry.

Further reading:

What is an ad hominem fallacy?

The ad hominem fallacy is a sin

Self-defeating claims and the tu quoque fallacy

Meta-sophistry

The associationist mindset

Very informal fallacies

The metaphysical presuppositions of formal logic