A Freeper's Introduction to Rhetoric (Part 1, Introduction and the Argument From Ignorance)

An argument, whatever its subject or sphere, is generally constructed in such a way as to prove that its conclusion is true. But any argument can fail to fulfill this purpose in either of two ways. One way it can fail is by assuming a false proposition as one of its premisses. We saw, in Chapter 1, that every argument involves the claim that the truth of its conclusion follows from, or is implied by, the truth of its premisses. So if its premisses are not true, the argument fails to establish the truth of its conclusion, even if the reasoning based on those premisses is correct. To test the truth or falsehood of premisses, however, is not the special responsibility of the logician; it is rather the task of inquiry in general, since premisses may deal with any subject matter whatever.

The other way in which an argument can fail to establish the truth of its conclusion is to rely upon premisses that do not imply the conclusion. Here we are in the special province of the logician, whose chief concern is the logical relations between premisses and conclusion. An argument whose premisses do not support its conclusion is one whose conclusion could be false even if all its premisses were true. In cases of this kind the reasoning is bad, and the argument is said to be fallacious. A fallacy is an error in reasoning.

The word "fallacy," however, as logicians use it, designates not any mistaken inference or false belief, but typical errors, that is, mistakes that arise commonly in ordinary discourse and that devastate the arguments in which they appear. Each fallacy, as we shall use that term, is a type of incorrect argument. An argument in which a mistake of a given type appears is said to commit that fallacy. Since each fallacy is a type, we can say of two or more different arguments that they contain or commit the same fallacy; that is, they exhibit the same kind of mistake in reasoning. An argument that contains or commits a fallacy of a given type may also be said to be a fallacy, that is, to be an example or instance of that typical mistake.

There are many ways in which reasoning can go astray; that is, there are many kinds of mistakes in argument. It is customary to reserve the term "fallacy" for arguments that, although incorrect, are psychologically persuasive. Some arguments are so obviously incorrect as to deceive and persuade no one. But fallacies are dangerous because most of us are, at one time or another, fooled by some of them. We therefore define a fallacy as a type of argument that may seem to be correct, but that proves, on examination, not to be so. It is profitable to study these mistaken arguments, because the traps they set can best be avoided when they are well understood. To be forewarned is to be forearmed!

Whether a given argument does in fact commit a fallacy may depend on the interpretation given to the terms used by its author. In a passage that appears to be fallacious, it may be difficult to determine out of context what meanings the author intended for the terms used. Sometimes the accusation of "Fallacy!" is unjustly leveled at a passage that was intended by its author to make a point missed by the critic — perhaps even to make a joke. We should bear such unavoidable complications in mind as we apply the analysis of fallacious argument to actual discourse. Our logical standards should be high, but our application of them to arguments in ordinary life should also be generous and must be fair.

How many different kinds of mistakes in arguments — different fallacies — may be distinguished? Aristotle, the first systematic logician, identified 13 types; recently a listing of more than 100 has been developed! There is no precisely determinable number of fallacies, however, since much depends, in counting them, on the system of classification used. We distinguish 17 fallacies here — the most common and most deceptive mistakes in reasoning — divided into three large groups, called a) fallacies of relevance; b) fallacies of presumption; and c) fallacies of ambiguity.

The grouping of fallacies is always in some degree arbitrary, because mistakes of one kind will bear close similarities to, and sometimes overlap with, mistakes of another kind. The placement of a given fallacious passage in one specific group is also often disputable, because there may be more than one mistake of reasoning in that passage. If one remains mindful of this unavoidable imprecision, gaining an understanding of the essential features of each of the three major categories and the specific features of its several sub-categories will be of much practical use. It enables one to detect the most troublesome errors in reasoning as they occur in ordinary discourse, and it promotes the logical sensitivity needed to detect related errors that may fall outside any one of these groupings.

When an argument relies on premisses that are not relevant to its conclusion, and that therefore cannot possibly establish its truth, the fallacy committed is one of relevance. "Irrelevance" may perhaps better describe the problem, but the premisses are often psychologically relevant to the conclusion, and this relevance explains their seeming correctness and persuasiveness. How psychological relevance can be confused with logical relevance can be explained in part by the different uses of language that we distinguished among in Chapter 4; the mechanics of these confusions will become clearer in the following analyses of the seven different fallacies in this group.

Latin names traditionally have been given to many fallacies; some of these — such as ad hominem — have become part of the English language. We will use here both the Latin and the English names.

The argument ad ignorantiam (from ignorance) is the mistake that is committed when it is argued that a proposition is true simply on the basis that it has not been proved false, or that it is false because it has not been proved true. We realize, on reflection, that many false propositions have not yet been proved false, and many true propositions have not yet been proved true — and thus our ignorance of how to prove or disprove a proposition does not establish either truth or falsehood. This fallacious appeal to ignorance crops up most commonly in the misunderstandings incidental to developing science, where propositions whose truth cannot yet be established are mistakenly held to be false for that reason, and also in the world of pseudoscience, where propositions about psychic phenomena and the like are fallaciously held to be true because their falsehood has not been conclusively established.

Famous in the history of science is the argument ad ignorantiam given in criticism of Galileo, when he showed leading astronomers of his time the mountains and valleys on the moon that could be seen through his telescope. Some scholars of that age, absolutely convinced that the moon was a perfect sphere, as theology and Aristotelian science had long taught, argued against Galileo that, although we see what appear to be mountains and valleys, the moon is in fact a perfect sphere, because all its apparent irregularities are filled in by an invisible crystalline substance — an hypothesis that saves the perfection of the heavenly bodies and that Galileo could not prove false! Legend has it that Galileo, to expose the argument ad ignorantiam, offered another of the same kind as a caricature. Unable to prove the nonexistence of the transparent crystal supposedly filling the valleys, he put forward the equally probable hypothesis that there were, rising up from that invisible crystalline envelope, even greater mountain peaks — but made of crystal and thus invisible! And this hypothesis, he pointed out, his critics could not prove false.

Those who strongly oppose some great change are often tempted to argue against the change on the ground that it has not yet been proved workable or safe. Such proof often is impossible to provide in advance, and commonly the appeal of the objection is to ignorance mixed with fear. Such an appeal often takes the form of rhetorical questions that suggest, but do not flatly assert, that the proposed changes are full of unknown peril. Policy changes may be supported, as well as opposed, by an appeal to ignorance. When the federal government issued a waiver, in 1992, allowing Wisconsin to reduce the additional benefits it had been giving to welfare mothers for having more than one child, the governor of Wisconsin was asked if there was any evidence that unwed mothers were having additional children simply in order to gain the added income. His reply, ad ignorantiam, was this: "No, there isn't. There really isn't, but there is no evidence to the contrary, either."

In some circumstances, of course, the fact that certain evidence or results have not been obtained, after they have been actively sought in ways calculated to reveal them, may have substantial argumentative force. New drugs being tested for safety, for example, are commonly given to rodents or other animal subjects for prolonged periods; the absence of any toxic effect on the animals is taken to be evidence (although not conclusive evidence) that the drug is probably not toxic to humans. Consumer protection often relies on evidence of this kind. In circumstances like these, we rely not on ignorance but on our knowledge, or conviction, that if the result we are concerned about were likely to arise, it would have arisen in some of the test cases. This use of the inability to prove something true supposes that investigators are highly skilled, and that they very probably would have uncovered the evidence sought had it been possible to do so. Tragic mistakes sometimes are made in this sphere, but if the standard is set too high — if what is required is a conclusive proof of harmlessness that cannot ever be given — consumers will be denied what may prove to be valuable, even lifesaving, medical therapies.

Similarly, when a security investigation yields no evidence of improper conduct by the persons investigated, it would be wrong to conclude that the investigation has left us ignorant. A thorough investigation will properly result in their being "cleared." Not to draw a conclusion, in some cases, is as much a breach of correct reasoning as it would be to draw a mistaken conclusion.

The appeal to ignorance is common and often appropriate in a criminal court, where an accused person is presumed innocent until proved guilty. We adopt this principle because we recognize that the error of convicting the innocent is far more grave than that of acquitting the guilty - and thus the defense in a criminal case may legitimately claim that if the prosecution has not proved guilt beyond a reasonable doubt, the only verdict possible is not guilty. The United States Supreme Court strongly reaffirmed this standard of proof in these words:

But this appeal to ignorance succeeds only where innocence must be assumed in the absence of proof to the contrary; in other contexts, such an appeal is indeed an argument ad ignorantiam.

It was too dang inconvenient to monitor more than one forum before, for me and for most others ...

Oh. That's not a bother for me. I use Mozilla, which has the "tabbed browsing" feature. From the "help" file:

Tabbed Browsing lets you open more than one web page in a single window. Each web page has its own tab across the top of a single Navigator window. Each tab appears on the Tab Bar. For example, you can visit mozilla.org, icq.com, and cnn.com within one window instead of three windows.

Every thread I'm watching gets its own tab, regardless of what forum it's in. (When you right-click on a thread, you have the choice of opening it as a new window, or as a net tab; I choose the 2nd option.) At the end of the day, I can save those tab settings, kinda like a single bookmark, and then re-open all those tabs -- with one click -- the next morning. Saves a lot of effort.

Mere artistic differences. I use Moz as well, but my preferred usage is to have the forum "new posts" in a browser window, and then open each article in a new tab as I come across it. That way, I can keep the forum itself separate from the articles, and I can also kill all the tabs in rapid succession while still leaving the forum window open. But in order to do that for multiple fora, I'd have to open a window for each forum, and open tabbed articles for that forum in that window - otherwise, I'll have forum tabs mixed in with article tabs, and I can't kill the article tabs bang-bang-bang, without possibly accidentally killing the forum tab also. This way, I have all new posts appearing in one tab, regardless of forum, and I can open all articles in new tabs, regardless of forum, so I can keep the single window and the organization style I prefer.

And if you have a three-button mouse, or a scrollwheel mouse where the wheel can function as a third button, you can set Moz to open links in a new tab just be clicking on the link with the middle button - saves time from right-clicking for the context menu. Even if you have a two-button mouse, you can get the same effect by holding down the CTRL key when left-clicking, if you check the appropriate box in Preferences -> Tabbed Browsing. Either way, it's much better than what the poor benighted souls stuck on IE get, IMO ;)

I maybe had too much eggnog at the office Christmas party (hic!) but I don't think that the "reasonable doubt" standard is an argument from ignorance.

Putting it into a nutshell, depending on the type of case, there are different ways that the burden of proof is allocated. In a civil case, the plaintiff has the burden of proof, and for most civil cases, the standard is "preponderance of the evidence." If the plaintiff proves that his version of the facts is more likely than the defendant's version, he prevails.

When you think of it, think of Justice holding her scales. They don't have to tip very much for the plaintiff to win, but if they are in equipoise, the plaintiff hasn't met the burden of proof and doesn't win.

In fact, the judge may not even force the defendant to put on evidence if the plaintiff's evidence isn't sufficient, but may dismiss the case on a motion to strike the evidence as being insufficient to make the case as a matter of law.

But if the plaintiff gets past the motion to strike, then the burden shifts to the defendant to prove his or her case.

In a criminal case, it works the same way, but the amount of weight that needs to be placed on the scales is far heavier. The plaintiff in a criminal case is the government, because a crime is an offense against the government. And the amount of weight that needs to be placed on the scales of justice in order to get past a motion to strike is far, far heavier than the 1% that is needed in a civil case. How much? There is not a percentage, but the evidence needs to be really, really strong. Strong enough that all by itself, without more, it's enough to meet the "reasonable doubt" standard in the mind of the judge.

It's called "reasonable doubt" because the standard doesn't require you to consider anything that's outside the scope of reason, such as aliens coming down and committing the crime.
Otherwise, the case doesn't go forward, but goes out on a motion to strike.

But if the case gets past the motion to strike, then defendant doesn't have to put on any evidence, but can let the jury decide based on the same evidence that the trial judge ruled was sufficient to get past the motion to strike.

This doesn't require the jury to be ignorant, but to have higher standards in a criminal case. If there are equally plausible explanations which are consistent with the facts and the evidence that mean that the defendant's innocence is a real possibility, then that should be sufficient to create reasonable doubt.

But a defendant in a criminal trial isn't found "innocent," he's found "not guilty." If it really were the same as "argument from ignorance," the failure to prove guilt would mean a finding of innocence. I think maybe in Scotland there is a finding of innocence but not in the USA or England.

But a defendant in a criminal trial isn't found "innocent," he's found "not guilty." If it really were the same as "argument from ignorance," the failure to prove guilt would mean a finding of innocence. I think maybe in Scotland there is a finding of innocence but not in the USA or England.

Ah, old Irving probably could have worded that section a little more clearly. It's really the presumption of innocence that's an argument from ignorance. We presume that the accused is innocent until proven guilty. But that presumption is itself an argument from ignorance - we don't, in fact, know that he is innocent, but we presume him to be innocent until proven otherwise. And insofar as that presumption may carry through to an acquittal, that acquittal may itself be an argument from ignorance - if the defendant does not present an affirmative defense to establish his own innocence, but is acquitted by virtue of the fact that the prosecution has failed to bear the burden of proof beyond a reasonable doubt, we still don't know that the defendant is, in fact, innocent - we simply default to an acquittal in the absence of evidence to the contrary, whether that acquittal is actually true to the facts or not. And in that case, the "not guilty" verdict is roughly equivalent to the verdict that the Scots have, but we don't - a verdict of "not proven".

But regardless of whether the verdict is a logical fallacy or not, we agree as a society to sacrifice a certain amount of logical cogency in the name of justice - as the authors paraphrase, we agree that it is better that 100 guilty men should go free than that one innocent man should be hanged. And in pursuit of that end, we agree to treat our ignorance as though it were, in fact, an affirmative conclusion, even though it isn't.

I think fallacies are overrated. I've been thinking of writing a book called "In Praise of Fallacies", or "My Favorite Fallacies", or "Fallacies We Can't Live Without" or somesuch. It would explain why some of the standard logical fallacies are actually indispensable in the real world.

I thought of this when I discovered to my horror that "the slippery slope" is considered a fallacy! This may be true in a strict deductive sense, but in order to make sense of the real world, you have to use a combination of deduction & induction, and place your bets accordingly. Things like the slippery slope (basically making a small concession to the opposition's argument, when the point being conceded turns out to imply a fundamental opposition point after all), or appeal to authority, or its flip side: ad hominem, can all be good tools to use in the face of real-world uncertainty.

The textbook article seems to recognize this somewhat, at least implicitly. I wonder how many formal fallacies are actually quite useful in this way?

(p.s. I'm sure I'll never get around to writing "In Praise of Fallacies", so anyone who wants to run with the idea, go for it. Mention me in the Acknowledgements. :-)

I discovered to my horror that "the slippery slope" is considered a fallacy

The slippery slope is almost universally appreciated; and it has various names in various cultures. In climates where they don't have snow-capped mountains, it's well-known as the "camel's nose in the tent." Among obese/diet-obsessed people it's known as "I've already eaten one potato chip, so now I'll finish off the whole bag." In basketball/rape situations it's known as "At first it was consensual." And among creationists, it's known as "If you admit any fact, no matter how well-established and obvious, then ..."

Similarly, when a security investigation yields no evidence of improper conduct by the persons investigated, it would be wrong to conclude that the investigation has left us ignorant. A thorough investigation will properly result in their being "cleared." Not to draw a conclusion, in some cases, is as much a breach of correct reasoning as it would be to draw a mistaken conclusion.

This is a liberal favorite; no amount of proof will suffice to win an argument with them. There will always be some "third way" pie-in-the-sky that will in future rescue their argument.

I use the example of the time I demonstrated a trick to my dad, and he snorted, "Once in a million!" I repeated the trick and he retorted, "Twice in two million!"

On any given issue any given person controls his own individual burden of proof; if you have faith that the earth is flat, then flat it will--at least in your own mind--remain. If on the other hand you have faith that the other person is illogical, then illogical they will--at least in your own mind--remain, mountains of evidence to the contrary notwithstanding. I would in fact suggest that our individual character is largely defined by what burden of proof we establish for propositions of various sorts.

At the risk of seeming unduly combatitive, under the presumptions of our Bill of Rights, I'd argue that the finding of "not guilty" should be the correct outcome of a criminal prosecution that failed to convict. If we were being logically severe, the phrase should read "not proved guilty", which would then properly imply nothing about the innocence of the party in question.

However, The principle of double jeopardy suggests to me that the law, in fact, reads a "not guilty" verdict as it stands, not as the Scots would have it, or as in "not proved guilty". I think US custom on this matter is morally correct. If the state, with it's virtually unlimited resources, chooses to bring an individual, with limited resources, to trial, and fails to make it's case, the morally correct conclusion, in my opinion, is "not guilty".

I think US custom on this matter is morally correct. If the state, with it's virtually unlimited resources, chooses to bring an individual, with limited resources, to trial, and fails to make it's case, the morally correct conclusion, in my opinion, is "not guilty".

So long as we don't confuse morally correct with logically correct, I agree. I think the distinction at issue here is the difference between legally innocent and actually innocent - the logician has the luxury (or burden) of considering absolute truth in such cases, rather than the morality of treating a finding of "not guilty" as being a finding of actual innocence. In the strictest logical sense, a finding of "not guilty" does not usually establish actual innocence - a certain former football player comes to mind here - but for the purposes of the law, we treat "not guilty" as establishing innocence. Whether that legal judgement is sufficient in the court of public opinion is another matter entirely - people are occasionally known to prefer logic to legality, depending on the circumstances.

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