by Cliff Walker
(revised October 2, 2000)
“An important scientific innovation rarely makes its way by gradually winning over and converting its opponents: it rarely happens that Saul becomes Paul. What does happen is that its opponents gradually die out and that the growing generation is familiarized with the idea from the beginning.”
Discussions with rank-and-the theists inevitably include logical fallacies. It is important to know the common ways that logic is misused, and how to counter them. More importantly, atheists, in their quest for truth, should know how to make a case without the use of such dishonest tactics. We are on a quest for truth; it should never be our purpose, as atheists, to give theists a snow job.
Premises form the basis for accepting a conclusion. If the premises are flimsy, the conclusion is equally unconvincing. As Thomas Paine said, “One doubtful thing cannot be admitted as proof that another doubtful thing is true.” 
The first two of the following sentences are the premises, the third is the conclusion:
(1) All men are mortal.
In more complex arguments, a conclusion can be used as a premise for a further conclusion.
Here is a large list of the common informal fallacies. Many of the examples given can fall into more than one category. Also, the division of faulty premises into various categories is not cut-and-dried.
An argument that uses its conclusion as one of its premises is most often called begging the question or circular reasoning. This classic case of circular reasoning has been used as an example for so long that we find only a few theists still using this fallacy: 
Is there a God?
In this fallacy, the premise, the Bible’s statement that God exists, derives its authority from the attempted conclusion, the existence of the God who allegedly wrote the Bible.
Theodore M. Drange gives another example of begging the question in his book Nonbelief and Evil. In his discussion on the concept of an afterlife, he distinguishes between what he calls technical death, and what he calls reducible death. “Technical death occurs when a person satisfies all the medical criteria for death but the body is not destroyed.” Reducible death “applies only to the case where the body and brain are destroyed.” Drange admits “that ‘reducible death’ does not mean ‘death without an afterlife.’ To define it that way would be question-begging, for it would make the term ‘afterlife’ self-contradictory.”  In other words, to define “reducible death” as “death without an afterlife” would be to refute the notion of an afterlife without an argument. Drange proceeds to discredit the notion of an afterlife through means other than defining it away in his premise.
Begging the question involves assuming the answer in stating the problem. For example, “We must institute the death penalty to discourage violent crime. But does the violent crime rate in fact fall when the death penalty is imposed? Or: The stock market fell yesterday because of a technical adjustment and profit-taking by investors — but is there any independent evidence for the causal role of ‘adjustment’ and profit-taking...?”  In other words, if we have not learned anything from the purported explanation, it is begging the question.
A subtle way in which theists beg the question is with the popular definition for the word atheist. An atheist, they often tell us, is “one who denies the existence of God.” However, when discussing the meaning of the word atheist, we must remember that an atheist is, among other things, a person who is engaged in an argument. The disagreement is between the theist and the atheist, and the very fact that atheists exist indicates that the controversy is far from resolved. So, then, to embrace either theism or atheism is to engage in the argument. Neutral observers do not support one position or the other.
Hopefully, a dictionary would remain neutral, but most dictionaries do not remain neutral when discussing the word atheist. Most dictionaries use language that presupposes the existence of “God” as fact, and describes an atheist as one who denies (the presupposed fact) of God’s existence. This definition Begs the Question and is biased in favor of the theistic position. Positive Atheism prefers the definition “one who lacks a god-belief.” This definition comes much closer to favoring no side of the argument, and goes no further than simply describing the atheist’s position in the debate.
“In addition to a ‘yes’ and a ‘no,’ the Universe contains a ‘maybe.’”
A false dichotomy assumes that only two (or only a few) alternatives exist when many alternatives actually exist. As Carl Sagan put it, this error results from “considering only the two extremes in a continuum of intermediate possibilities.”  To avoid extremist, black-and-white thinking, Robert Anton Wilson divides statements into several categories: True; False; Relatively True; Self-Referential; Meaningless; Indeterminate; Strange-Loop; Game-rule. 
Alcoholics Anonymous presents its captive audience of impaired people the following false dilemma: “To be doomed to an alcoholic death or to live on a spiritual basis are not always easy alternatives to face.... But after a while we had to face the fact that we must find a spiritual basis of life — or else.”  However, studies show that over 70 percent of formerly addicted people cleaned up on their own, without help of any kind. There also exist many nontheistic methods for overcoming addiction. “Believe or die!” is not one’s only choice here.
A popular form of this ruse is the fallacy of negation, the notion that if we discredit one side of an argument, the observer is forced to accept the other. This is a pet ploy of many creationists, who claim that life either was divinely created or it evolved. “Then they spend the majority of their time discrediting the theory of evolution so that they can argue that since evolution is wrong, creationism must be right. But it is not enough to point out weaknesses in a theory.... A new theory needs evidence in favor of it, not just against the opposition.” 
Molleen Matsumura makes this problem easy to understand: “Finding a problem in one theory doesn’t prove that another is correct. Suppose I ask you and your friend what kind of fruit I have in a paper bag. You guess that it’s an apple, and your friend guesses that it’s a cherry. Then I say, ‘I’ll give you a hint — there’s one big seed in the center.’ I’ve just proved that you were wrong, but that doesn’t make your friend right. It could be a peach or an apricot!” 
Carl Sagan brings special attention to a form of false dichotomy that pits short-term goals against long-range goals: “We can’t afford programs to feed malnourished children and educate pre-school kids. We need to urgently deal with crime on the streets.” “Why explore space or pursue fundamental science when we have so huge a budget deficit?” 
Black-or-white thinking abounds in popular thought: “Either you love your country or you hate it.”  “He who is not with me is against me.”  “If you’re not part of the solution, you’re part of the problem.” 
To prevent this problem, Sagan says: “Spin more than one hypothesis ... think of all the different ways in which it could be explained. Then think of tests by which you might systematically disprove each of the alternatives. What survives, the hypothesis that resists disproof in this Darwinian selection among ‘multiple working hypotheses,’ has a much better chance of being the right answer than if you had simply run with the first idea that caught your fancy.”  He adds: “This is a problem that affects jury trials. Retrospective studies show that some jurors make up their minds very early — perhaps during opening arguments — and then retain the evidence that seems to support their initial impressions and reject the contrary evidence.” 
The Straw Man fallacy is a rhetorical technique that caricatures the opponent’s position to make it easier to attack. The metaphor is of someone who builds a straw man or scarecrow and then knocks it down and gloats over his accomplishment. This is not much of an accomplishment, though, because the idea attacked is not the idea the opponent held in the first place. The one using the straw man ploy attacks his own understanding of his opponent’s opinion — not his opponent’s actual position.
Creationists often make false claims about what the theory of evolution states, saying, according to Carl Sagan, that scientists “suppose that living things simply fell together by chance.” This formulation, says Sagan, “willfully ignores the central Darwinian insight, that Nature ratchets up by saving what works and discarding what doesn’t.”  One that we hear often in our Letters section suggests that “there is no real support for the idea that once upon a time there was only hydrogen gas and then became people.”
The straw man approach is often used in conjunction with other logical and rhetorical fallacies. If someone describes his opponent’s position in a way that sounds patently absurd (something that no one in their right mind would believe), making his own position sound too good to be true, check to see if that is the opponent’s actual position. If not, we have an example of the straw man.
With the reductio ad absurdum approach, one carries the opponent’s position to its logical end, without mentioning that this is not the inevitable result of the opponent’s viewpoint. Of course, if the consequences of an argument are inevitably absurd, the argument is flawed. However, we must be careful, because “pushing an argument to its limits is a useful exercise in critical thinking; often this is a way to discover whether a claim has validity, especially if an experiment testing the actual reduction can be run.” 
One way some Christians use this against the atheistic position is to say, “Atheists have no source for their morality; therefore, what’s to stop them from committing rape and murder.” This ignores the fact that most atheists think long and hard about right and wrong and do have a source for their morality: Reason. It also disregards the atheistic belief that this is the only life anyone gets. “With this recognition of the finality of death, no one should willingly withhold acts that would bring benefits, joy or happiness to others. 
The slippery slope fallacy often constructs a scenario leading to an end so extreme that one should never take the first step. “Eating Ben & Jerry’s ice cream will cause you to put on weight. Putting on weight will make you overweight. Soon you will weigh 350 pounds and die of heart disease. Eating Ben & Jerry’s ice cream leads to death. Don’t even try it.”  While it always takes that first scoop (or whatever) before someone will die of complications from obesity, this is rare. “The consequence does not necessarily follow from the premise. 
Carl Sagan says that the reductio ad absurdum is commonly used by both sides in the abortion debate. One side says, “If we allow abortion in the first weeks of pregnancy, it will be impossible to prevent the killing of a full-term infant.” The other replies, “If the state prohibits abortion even in the ninth month, it will soon be telling us what to do with our bodies around the time of conception.” 
Garrett Hardin, pioneer in the science of human ecology, says that the slippery slope is unavoidable in this and many debates. Asked about the objection that legalized abortion “puts us on the slippery slope to euthanasia, assisted suicide, and elimination of the ‘unfit,’” he responds:
“First let’s look at the concept of the slippery slope. Every ethical decision puts you on the slippery slope. You just have to live with it. For example, we used to have a speed limit of 65 mph. That’s a slippery slope for God’s sake. No matter where you put the speed limit, people want to push it up and up and up. The only completely safe speed limit is zero mph. Anything above that will get pushed up and up. What do we do? We draw an arbitrary line and set the speed limit at a certain level. Back in the days of the old 65-mph limit, you couldn’t prove statistically that 66 was more dangerous than 65.
“In the specific case of abortion, the matter is particularly easy in that no woman wants a late abortion. Once abortion was made legal, the age of the aborted fetus went down. The slope slipped in the other direction. If we legalize RU-486 and other similar new drugs, the age will fall to one week or less and start approaching zero. The slippery slope will slide in the other direction. The only reason we have late abortions is because we make early abortion difficult.” [68a]
The false cause fallacy assumes that two events are causally connected when they are not. The Latin post hoc, ergo propter hoc, means, “After this, therefore because of this.” The mistake comes from thinking that because one event took place after another, the second was caused by the first.
“At its basest level, it is a form of superstition. The baseball player does not shave and hits two home runs. The gambler wears his lucky shoes because he has won wearing them in the past.... As Hume taught us, the fact that two events follow each other in sequence does not mean they are connected causally.” 
Christians often say that because Madalyn Murray-O’Hair removed prayer from the schools (she didn’t, the Supreme Court did this in 1963), morality in America has been on the decline. This is the basis for the reasoning behind the United States House of Representatives’ move to allow posting of the Ten Commandments in the schools. However, it has not been established that there is a moral decline in the United States; many think we have made vast improvements in areas such as civil rights since 1963. Even if it could be shown that there has been a moral decline, they still would need to show the cause-and-effect relationship between school prayer and a nation’s moral standing.
Sometimes there exists a confusion between correlation and causation. Scientific studies can fall prey to such confusion. “In 1993 a study found that breast-fed children have higher IQ scores. There was much clamor over what ingredient in mother’s milk increased intelligence.... But soon researchers began to wonder whether breast-fed babies are attended to differently. Maybe nursing mothers spend more time with their babies and motherly vigilance was the cause behind the differences in IQ.” 
Such confusion can affect public policy. “Children who watch violent TV programs tend to be more violent when they grow up. But did the TV cause the violence, or do violent children preferentially enjoy watching violent programs? Very likely both are true.”  Meanwhile, many American subcultures are polarized on this issue.
Non sequitur is Latin for “it doesn’t follow.” This means that the conclusion does not follow from the premises. Politicians will pronounce a non sequitur until it is repeated so often that very few bother to think critically about it. For example, “’Our nation will prevail because God is great.’ But nearly every nation pretends this to be true; the German formulation was ‘Gott mit uns.’” 
Someone using the non sequitur fallacy may simply fail to see other possibilities. At times, though, someone with an agenda is fully aware that the masses tend to accept any oversimplified formula that is pontificated by a smooth operator. Such operators know what their audiences want to hear, and their rhetoric is often filled with the non sequitur and other similar fallacies of reasoning. After all, “The pew cannot reply to the pulpit, you know; it has just to sit there and take it.” 
“An argument from analogy claims that things which resemble one another in certain respects resemble one another in further respects.... The success of such arguments depends upon the nature and extent of the similarities between the two objects. The greater their dissimilarities, the less convincing the argument will be.... Consequently and argument from analogy can be successful only if the dissimilarities between the things being compared are insignificant.” 
Evangelistic anecdotes tend to be replete with faulty analogies (besides being, in general, insipid oversimplifications). Someone sent Positive Atheism a story about an atheistic barber  who was walking through town with a preacher. The barber said, “If God was as kind as you say, He would not permit all this poverty, disease, and squalor. He would not permit disease. He would not allow these poor bums to be addicted to dope and other character-destroying habits.”
The preacher pointed out a particularly unkempt man with matted hair, and said, “You can’t be a very good barber or you wouldn’t permit a man like that to continue living in this neighborhood without a haircut and shave.”
The barber replied, “Why blame me for that man’s condition? He has never come in my shop: I could fix him up and make him look like a gentleman!”
The preacher, with a “penetrating look,” said, “Then don’t blame God for allowing the people to continue in their evil ways, when He is constantly inviting them to come and be saved.”
This analogy breaks down because the “God” character is (allegedly) omnipotent, and (as the myth goes) could have been more diligent in protecting his children in the Garden of Eden from harm and from enemies such as the serpent. This god shows no willingness to make good; therefore, he is, ultimately, the author of human sin. The barber in this tale is not omnipotent, but did express willingness to do what he could to change the situation.
Secondly, the argument from the existence of evil, properly stated, includes the existence of such evils as earthquakes, disease, premature death, and other things not brought on by any human acts. The barber analogy ignores this aspect of the argument entirely.
Faulty analogies are not restricted to abstract ideas, such as the Christian scheme of salvation. Any two things can have some features in common: “’Astronauts wear helmets and fly in spaceships. The figure in this Mayan carving seems to be wearing a helmet and flying in a spaceship. Therefore it is a carving of an ancient astronaut.’ Although features of the carving may bear a resemblance to a helmet and spaceship, they bear a greater resemblance to a ceremonial mask and fire.” 
“You know sometimes words have two meanings,” as the song goes.  Equivocation occurs when a person changes the meaning of a word during the course of the discussion. This is commonly done with religious terms.
Theist: “I have faith in the lord Jesus Christ, and because I have this faith he will take me to Heaven when I die.”
The theist (aside from dodging the question) is trying to convince the atheist that “faith” is nothing unusual, that even atheists have faith. However, according to mainstream Christian teaching, the “faith unto salvation” that one has in Jesus is entirely different than simply trusting a situation or a person, or believing that a certain event occurred in history.
Another classic example of equivocation is when God (allegedly) told Adam and Eve, “in the day that thou eatest thereof thou shalt surely die” (Genesis 2:17). Because (according to the story) Adam and Eve lived many hundreds of years after they ate, it became necessary for Christian apologists to change the meaning of the word die from the obvious meaning, and give it a new meaning, unique to Christian apologetics! Stuff like this happens when you are called to defend a presupposition such as the notion of biblical inerrancy.
“In logic, the hasty generalization is a form of improper induction. In life, it is called prejudice. In either case, conclusions are drawn before the facts warrant it.”  “You are guilty of hasty generalization, or jumping to conclusions, when you draw a general conclusion about all things of a certain type on the basis of evidence concerning only a few things of that type.”  Someone once wrote complaining that we had called author Fyodor Dostoevsky an atheist. We did no such thing! Turns out that our inclusion of a few Dostoevsky quotations in our collection constitutes, to this reader, the implication that he was an atheist. No, we put those quotes in because we thought they were cool quotes and that the ideas expressed by them might be useful or inspiring or challenging to our readers!
It is easy to see how primitive humans could conclude that the earth was flat. They jumped to conclusions, and this is understandable. However, followers of Pythagoras (582?-500? B.C.E.) were the first to consider the earth a globe revolving with the other planets around a central fire.  Aristotle (384-322 B.C.E.) elaborated on the Pythagoreans’ proof that during a lunar eclipse, the earth’s shadow is always curved by observing that “there are some stars seen in Egypt and in the neighbourhood of Cyprus which are not seen in the northerly regions; and stars, which in the north are never beyond the range of observation, in those regions rise and set.”  The ancients also observed that when a ship sails to sea, the hull disappears first and the mast last, and some, by this, concluded the sphericity of the earth. Eratosthenes (276?-196? B.C.E.) measured the circumference of the earth with extraordinary accuracy by determining astronomically the difference in latitude between the Egyptian cities of Syene (now Aswân) and Alexandria.  All this this was known long before Christ is alleged to have lived.
There is no excuse for Christian theologians of a later time who reverted to the flat-earth view. Had they simply made the mistake of jumping to conclusions, they would have been far less culpable. The Christians, however, used the Bible as a science book, and the Bible most definitely portrays the earth as flat.  They had no excuse, because the data had been in for many centuries. This is what happens when a dogmatic religion gains political power. The Christians suppressed and persecuted genuine scientific inquiry for over fifteen centuries, and many powerful Christians and Christian groups continue to thwart scientific progress today.  This was not simply a hasty generalization, but willful and malicious disregard for truth.
Columbus “discovered” America  72 years before Galileo was even born.  Magellan circumnavigated the globe  42 years before Galileo was even born. Nevertheless, the Inquisition of the Roman Catholic Church persecuted Galileo for his view that the earth is a globe, among other things. It wasn’t until October, 1992, that a papal commission acknowledged the Vatican’s error in condemning Galileo for his “heresy.”  This was not simply a hasty generalization, but willful and malicious disregard for truth.
An argument involves suppressed evidence when the person initially making the claim knowingly and deliberately fails to reveal a crucial fact that would refute his or her position. Carl Sagan describes how “an amazingly accurate and widely quoted ‘prophecy’ of the assassination attempt on President Reagan is shown on television; but — an important detail — was it recorded before or after the event?” This has been shown to be the case: the “prediction” was made after the fact.
Those who merely repeat a claim that contains suppressed evidence are not necessarily guilty of suppressing evidence. A case in point is the recent popularity of the Jesus-Chalk Hoax,  a tale traveling the Internet which concerns a nonexistent philosophy professor at the University of Southern California. Besides slanderously portraying atheists and academics as being viciously intolerant of Christians, this tale is a variation of another tale that appeared in a 70-year-old book of allegedly miraculous accounts.  Some Christians are appalled that such dishonest tactics would be employed to convince people that Christianity is true, but it is hard to fault someone who innocently passes something on without checking it out. The culpability increases when people spread the story knowing it is a hoax (or at minimum, questionable). There is no excuse at all, however, for the one who started the hoax.
So-called pious frauds were a staple of the Christian Fathers of the fourth century. Lecky describes how Conyers Middleton exposed this phenomenon in 1784: “He contended that the religious leaders of the fourth century had admitted, eulogised, and habitually acted upon principles that were diametrically opposed, not simply to the aspirations of a transcendent sanctity, but to the dictates of the most common honesty. He showed that they had applauded falsehood, that they had practised the most wholesale forgery, that they had habitually and grossly falsified history, that they had adopted to the fullest extent the system of pious frauds, and that they continually employed them to stimulate the devotion of the people.” 
John Young reported about current hoaxes which are broadcast far and wide among Christian circles, and especially on Christian television. One story, passed on by former Moral Majority paladin Cal Thomas, was that a fourth grader “had purchased and given to two classmates new lunch boxes with the note ‘God loves you in Christ.’ The story goes that the girl was reprimanded by her teacher, told, according to Thomas, ‘she must not write or even speak about religion in school.’ It would be an abomination if true. The true abomination is that it’s a lie. A district spokesperson, interviewed by phone, said Ashley Pollack doesn’t exist. Or, if real, Ashley never attended Millcreek schools.” 
Young continues: “Then in Texas there was 5-year-old Shannon. According to the 1992 story passed on by Pat Robertson’s 700 Club, she’d been told by her teachers in Kingsville she couldn’t say grace over her meal. One technical problem with that story. Shannon didn’t exist. Or if she existed, she didn’t attend Kingsville schools. But Kingsville, and all other public schools, took a mighty airwave thrashing.” 
Another hoax being perpetrated upon Americans is the notion that the United States is a “Christian nation.” Bogus quotations from James Madison and others are disseminated by history revisionist David Barton of WallBuilders, Inc.,  and continue to be spread long after it has been shown that these quotations cannot be found in any known writings or archives  — long after Barton himself asked his followers to stop using them. These reports continue even after a federal court has ruled that “Barton’s [revisionist] materials are inappropriate for use in public schools.”  This arrogance only shows that the fourth century is still with us. A callous disregard for truth still thrives in the quest to make the Christian religion appear credible before the public.
Such stories get repeated without any attempt to verify them, probably because they fit the popular Christian stereotype of those who advocate separationism. Then they end up being repeated on the floor of the Senate and the House of Representatives with the same disregard for verification. As a result, ideas such as the Religious Liberty Protection Amendment  will become law, and Christians will be given “protection” they don’t even need — at the expense of those Americans who aren’t Christians. All because someone deliberately suppressed evidenced along the way.