Question: Some months ago, in an article on evaluating evidence, you mentioned "logical fallacies." Could you explain what they are?
Answer: Perhaps it is best to start by defining logic as "the correct mental evaluation of external reality and previously acquired concepts." A man's mind starts out as a sort of "empty slate," upon which he makes "notes" about the things around him. Once he has made a few such "notes" he may begin to compare each in the light of the others: Is one thing the same, different, or similar to another thing? Is a certain statement or conclusion true or false? Did one action cause another, or did they arise from a common origin, or happen independently?
We can think of logic as the set of rules necessary to make these evaluations correctly. "Logical fallacies," on the other hand, are rules that lead to false evaluations.
While we start to develop logical skills at about the time we learn to talk, most people don't get formal training in logic until they begin high school mathematics. In a sense, this is unfortunate, in that most mathematical logic is different from the logic required in "real world" evaluations. Mathematics -- geometry is a particularly good example -- generally starts out with a set of ruules that are agreed upon in advance: one who has memorized all of the axioms and postulates, and applies them logically, will always arrive at the correct answer. Mathematicians may recognize that their rules do not exactly describe the real world, but they have agreed to ignore the discrepancies.
Most other disciplines (and statistical mathematics) require us to formulate our rules based on our observations. For example, in past centuries men like Galileo and Newton studied the motions of moving bodies. They repeated their experiments over and over, and determined that moving bodies always seemed to move the same way under the same conditions. The resulting "laws of motion," formulated mathematically, seemed to describe the motions of all moving bodies -- so much so that people began to apply them much like the axioms and postulates of geometry. People of Galileo's time had inherited a similar set of "laws" about motion from the pre-Christian Greek philosopher Aristotle. Aristotle's "laws" didn't work very well, but people tended to accept them anyway because they came from the great Aristotle!
Taking Aristotle's unsupported word on the movement of bodies was the logical fallacy of "Appeal to Authority" -- taking something to be true because an important person says it is true. Aristotle was an extremely great thinker, whose philosophy is still held in high regard, he just didn't verify his theories about moving bodies and they turned out to be wrong -- yet accepted for many centuries because of his great authority.
Galileo and Newton took the additional step of experimentally measuring the motions of bodies, not just thinking about the motion of bodies as Aristotle apparently had. In high school physics at the turn of the twentieth century, students repeated Galileo's and Newton's experiments, learned Newton's "laws" and took them as absolute truth. (Back to this in a moment!)
Some disciplines are not always clear cut. For example, some chemical reactions, starting with the same ingredients seem to "go in different ways," producing one product some of the time and another product at a different time under the same conditions. Of course, it is possible that the chemists have not yet considered all of the relevant conditions.
Our physics student in 1900 would probably have been rather dogmatic about the "laws" he had learned from Isaac Newton. After all, they were "laws"; they must be absolute; and we got them from Sir Isaac himself. Yet, in the early 1900s, Albert Einstein came along and demonstrated that Newton's "laws" didn't work correctly for very massive bodies or for those moving at very high speeds. His "theory of relativity" made some refinements to explain these discrepancies. Not long thereafter, it was discovered that neither Einstein nor Newton properly predicted the behavior of really tiny bodies or "packets" of energy. People who had accepted the physics of Newton had committed the logical fallacy of "Hasty Generalization" -- they had assumed that by examining some cases of motion, they had accounted for all cases. In this instance, the error applied only to extreme cases, but lesser people than Newton have been known to make much less supportable generalizations from the evidence presented to them.
Honest scientists are quick to admit that their "laws" are not infallible -- they are indeed, "theories," reflecting their best attempts to generalize what they have observed. The are always humbled by the impossibility of observing every case of everything that ever happened. It is unlikely, but someone, somewhere, somewhen, may have witnessed an apple falling up or water freezing when heated -- or maybe such things have happened when no one was looking! In any event, determining all of the relevant conditions is a pains-taking process.
Actually, the physical scientists have it much easier than most people in trying to avoid logical fallacies. A great deal of human endeavor takes place without the benefit of experimental techniques. Testing the truth of a religious, philosophical, economic, historical, or social (to name just a few categories) statement is almost always more uncertain than predicting the outcome of an experiment in chemistry or physics. Human affairs contain many more variables than chemical experiments, there is often a great deal of extraneous information available, and it is rarely clear just what decisions must be made. Trying to formulate "laws" to predict human behavior, to evaluate the truth of people's statements, or to compare the behavior of one with another is much more difficult than coming up with "laws" about atoms or molecules.
Sometimes people are careless in their thinking, and sometimes their purpose is deception. Often enough, when we are reading or listening for entertainment, we are "off guard" as to the logic or illogic we are receiving. Nonetheless, experience has given us a list of mistakes that people often make in their logical judgements, beyond the ones already mentioned. We will try to describe some of them briefly below:
"Right for the wrong reason": Sometimes people reach a correct conclusion through illogical means. This is dangerous for a critic may then be able to "disprove" the correct conclusion by pointing out the flawed logic used to arrive at it. "Smith is too ugly to be a theologian, therefore he is not" may reach the correct conclusion that Smith is not a theologian, but ugliness is no proof of this.
"Ad hominem" (against the man:) Attacking the person instead of his abilities or qualifications: "He's too ugly to know anything about theology." Obviously ugliness does not keep one from studying about God. Often the ad hominem argument is set up less directly by telling a story that makes the victim seem ridiculous without directly calling him names.
"Appeal to Pity" or "Force": "You've just got to believe me or I will die." "You've just got to do what I ask or I'll beat you."
"Appeal to the Masses": "Everyone knows that the Moon is made of green cheese." "Nobody wears hats anymore." In reality, even an overwhelming majority is quite capable of being wrong.
"Straw Man": Claiming that one's opponent holds a certain position that is easy to attack, successfully attacking it, and then claiming to have defeated one's opponent. "Smith says that the sky is green. Just look up in the sky and you can see what a fool Smith is." (Only Smith never claimed that the sky is green.)
"Accidental inclusion": Rules applied beyond the intent of the rule maker. Speed limits, for example, are often not intended to apply to emergency vehicles. Ticketing a fire engine on the way to a fire might be an "accidental inclusion."
"Appeal to ignorance": Urging belief in something solely because of a lack of evidence to the contrary. "No one has ever proved that the tooth fairy is a mythical being, therefore it is reasonable to believe in the tooth fairy."
"Ad Hoc theories": "Ad hoc" doesn't translate well into English, but it describes a theory that tries to explain just the exact situation at hand (i.e. not a broad spectrum of possible situations), often with little thought or research: "Who broke the window? The wicked window witch, of course.")
"Poor analogy": "My last car was red and I drove it for 150,000 miles. Since I want another long lasting car, I am buying another red one."
"Posturing" (appeal to imaginary status): Trying to appear above or more legitimate than one's opponent by asserting some nonexistent or inadequate authority. "Our teaching is most truly Catholic, for we are the Society of Jesus." "We have no need of accreditation for we are members of the Ivy League." "You have no right to ask me 'why?' for I am a priest and it is true because I say so."
"But not for the gander": Criticizing the defects of the opponent, while ignoring the same faults in one's self. There may be some implicit or explicit "posturing" in order to minimize self scrutiny. "We Republicans are the Party of the Constitution; the Democratic Party ought to be brought to justice for the unconstitutional laws they passed when in power." Sometimes the claims may be valid, but always they are hypocritical.
"Ignoring evidence": The speaker simply doesn't tell everything he knows because it would hurt his position. "Smith is a great man -- compassionate and highly experienced -- he ought to be the next mayor of Podunk." (Except he is still in jail for taking bribes last time he was mayor.)
"Fictitious Opposition Groups (FOG)": Large scale fraud is easier to perpetrate if one owns the opposition. A good FOG will give the appearance of well balanced media coverage while allowing meaningful opposition to be excluded. It may attract financial contributions, and waste the time and resources of those who would otherwise join a real opposition group. The FOG can always be counted to capitulate when the chips are down, or by simply acting ineffectively it can remain around to (not) fight another day. Generally speaking, only the already influential will enjoy the opposition of a FOG.
"Citation of non-existent evidence": Desperate or lazy people may try to support a claim by referring to evidence that doesn't exist, but is hard to verify at the moment. Readers and listeners are often correspondingly lazy in not verifying what they have been told, particularly if the source seems authoritative. Ecclesiasticus x: 6-8 says nothing about the kosher food laws, the 14th Amendment grants no right to abortion, and Summa Theologica III-III Q.5 a.6 doesn't exist -- but you might not know that without looking.
"Purposeful mistranslation": A lot of people can't read Greek, Latin, or any foreign language. Even if they can read a little of the language, translation is an inexact enough thing that meanings can be shaded to serve the speaker's purpose.
"Flat-out lying": This shouldn't need description, but remember that some people lie very well without any visible cues. Remember too that the most believable lies are often very close to the truth.
Construction & Causality
"Missing the point": A valid argument is presented, but an incorrect and only vaguely related conclusion is drawn. "The Constitution can be amended, and has been dozens of times, therefore the Constitution has no fixed meaning."
"Red Herring": The speaker changes the subject under discussion, presents a valid argument about the new subject, and claims to have proved his point about the original subject. "We need child safety locks on guns. Children represent the future of our nation. The next Einstein or Newton may come from our young. No one can dispute the importance of having such great intellectuals in society, so, therefore, we need safety locks on guns."
"Correlation is not causality": Effects come from causes, so they can usually be paired together -- but just because things regularly seem to be paired is not adequate to determine that one causes the other. Coincidences do happen, particularly in the short run: "The team has lost every game in which the band played 'America the Beautiful,' so we must stop the band from playing it if we are to have a winning season." And sometimes both items in a pair are the effects of a common cause, rather than one being the cause and the other being the effect: "Babies are born shortly after the storks build their nests, therefore storks must bring the babies."
"Post hoc (After, therefore because of)": Effects always follow their causes in time. The mere sequence of events may lead one to believe that they are correlated and that one has caused the other. "The Spanish government arrested Smith right after a visit from the American ambassador" might suggest that the ambassador had something to do with Smith's arrest, yet the visit could have been absolutely unrelated. Note that the music of the band or the visit from the ambassador might have had claimed effect, but more is needed to prove the case. Relying on correlation or sequence in time to "prove" something leaves one open to having one's opinions discredited as illogical even though they may be correct.
"Slippery slope": An event may be the cause of a second event, which in turn may cause a third, and so on. Arguing that if a first event is allowed to take place, a specific Nth event will surely take place is often beyond our capabilities of prediction. The first domino might actually take out the thirty-sixth domino, but then again it might not.
"Begging the question": Claiming to prove an assertion by merely restating the assertion in different words. "Capital punishment is evil because it is an immoral and inappropriate way for society to deal with criminals." "Capital punishment is good because it is a moral and humane way for society to deal with criminals." Neither statement says anything about the legitimacy of capital punishment; both statements simply restate their claim with alternative ways of saying "good" and "evil." Sometimes "begging the question" consists of a longer chain of seemingly connected ideas, with the assertion appearing both at the beginning and the end of the argument: "Capital punishment is evil. Man has had to struggle against evil since the time of Adam and Eve. Throughout this struggle civilized people have always recognized that murder is evil. Since it is a crime against civilized mankind, capital punishment is evil."
"Dilemma in answering": It is possible to pose a question in such a way that any simple answer is embarrassing or even incriminating: "Have you stopped beating your wife?" "Where did you hide the money you stole?" "Why didn't you do something more useful with the money you wasted on your drug habit?"
"False splitting": We often try to get our way by proposing an undesirable alternative to what we want to do: "If you don't let me smoke marijuana, I will become a very irritable person and will embarrass both of us wherever we go." Presumably, there is some third way, but the speaker would like to keep it out of the conversation in order to gain approval to pursue the first way.
"Composition:" Transferring an attribute of a part to the whole. "This apple is delicious, therefore the whole barrel is delicious."
"Division": Transferring an attribute of the whole to a part. State College is an excellent university, noted for its scholarship, therefore all of its students are excellent scholars.
"Ambiguity": Using words that have several meanings in a way that may mislead: "I am loyal to the Magisterium" might mean loyalty to the current Pope, loyalty to the authority possessed by the Popes over the centuries, or loyalty to what has been decreed by the Popes. Using the same word several times in an argument, but with different meanings each time is usually called "equivocation": "The weather bureau says that the mean temperature was 78 degrees yesterday; all other temperatures, not being mean, must have been nice."
"Amphiboly": A grammatical ambiguity, usually caused by excessive brevity: "I've named Tom and Alice to be guardians of Richard and Sally" could mean that they will exercise joint custody over both children, or that Tom will be Richard's guardian and Alice will be Sally's.
"Euphemisms": It is possible to make something seem good, bad, or neutral by giving it a name that has the appropriate connotation: "Women's choice" and "infanticide" give relatively opposite emotional connotations to "abortion," while "termination" sounds relatively neutral. The baby is just as dead in all three cases.
It is not always easy to defect fallacies in what we hear or read. Being familiar with the various kinds of fallacy is useful. Taking a course in "informal logic" would be good for those with the time and inclination. Perhaps the best way to avoid being fooled by others in speech or writing is to force one's self to speak and write logically. If you take the time to logically evaluate the things you say and write, you will more quickly learn to recognize the fallacies of others.
Remember that the truth is important -- so important that our Lord Jesus Christ identified the Holy Ghost as "the Spirit of truth," and Himself as "the way, the truth, and the life."
January 2001 Update:
"Bulverism:" Judging the truth of an argument based on the perceived motives of the speaker, rather than on objective facts. Trying to determine why he is wrong, before determining that he is wrong. "He is a Protestant, so he must be wrong about the Immaculate Conception." Named for the imaginary inventor Ezekiel Bulver, and attributed to C.S. Lewis.
"Grammatical obfuscation:" Purposefully making writing or speech unclear. Humans can only absorb so much at a time. Ideally, sentences are relatively simple, clearly expressing a concept. Related concepts are grouped together in paragraphs, each showing how the concepts are related, and how they logically evoke a conclusion. Paragraphs are presented in such a way as to progress from an introduction to a conclusion. Larger works may need to be divided into chapters or sections and chapters in order to be able to present information in manageable portions. One who prefers not to be understood may simply speak or write without organizational structure.
"Loquacious obfuscation": Literally, making things unclear with lots of words. Sentence length (and intensity) can be increased through the use of extra adjectives or by building complex sentence structures. Writing about the "no good, low down, dirty, rotten, awful, conniving, deceitful, crooked, Mayor of Podunk" probably doesn't give us any real information about the mayor, but it does use up some of our "span of comprehension" of what has been said. Writing endless paragraphs about the mayor, particularly if they develop no logical theme, will confuse or put most people to sleep. Some writers will do this sort of thing, and conclude with a paragraph claiming that "this (all of the paragraphs that you slept through) clearly proves the point I made in my introduction." Frequent recourse to "boilerplate" texts and lists is often indicative of loquacious obfuscation. Sometimes the loquacious will tell you everything they know, hoping that you will find something that you will believe in line with their conclusion.
"Dynamic obfuscation": Frequently changing the topic under discussion without ever proving anything or reaching a conclusion. Usually followed by claiming to have proved everything.
"Interlaced obfuscation": Placing meaningful information in the midst of large volumes of meaningless information. This may be done when there is a need to place information "on the record" but there is a hope that no one will see and act upon it. This gives the writer the ability to say later, "I told you but you ignored what I said."
"Nit picking offensive": Normally, people agree what positions are being taken at the beginning of a debate. They don't hold each other to precisely restating their position each time it must be named in discussion. The "nit picker" will accuse his opponent of inconsistency or error each time he fails to make a precise restatement. The "nit picker" will also object to imprecise generalizations, even though the imprecision has no effect on the argument.