I am a skeptic. I have a hard time believing in things that aren't proven, and I still don't necessarily believe in things after they're proven, for the reason that 'proof' is a very subjective term. I love to debate and I do my best to remain logical as opposed to emotional during the exchange.

The following is a list of terms that are often used by skeptics in debates. These include logical fallacies and other terms often used to debunk charlatans and liars.

It is always a good idea to have an understanding of how not to be duped in an debate. This list will show you many of the trick, used purposely or not, that people use to help their faulty arguments.

Ad Hoc Hypothesis

Definition: Explaining away facts that are contrary to your hypothesis.
Example: A psychic claiming that their ESP doesn't work today because of a negative vibe caused by an overseas conflict.
Explanation: So called "psychics" often use this technique when they fail to make an accurate prediction. They justify their ability to do this because they often claim that their psychic abilities are not exact science. The major problem with this is that if you are allowed to write off all your failures whenever you want, you will always have a much higher success rate. This is something I would love to have on a math test. "I got the first question wrong? Well that's because of the loud noise outside the room, so it shouldn't count against my final grade." Similar to "special pleading" where an unusual excuse is made to help prove a failing argument.

Appeal to Authority

Definition: Citing the works of an 'authority' figure and using it as evidence.
Example: Doctor Fred says that this machine will make you lose ten pounds a week without diet or exercise.
Explanation: Authority figures don't always agree on every issue and, like all humans, they can make mistakes. Appeal to authority is often used in infomercials to sell you junk. Just because an authority figure says it will work doesn't mean it is proven to work. The evidence must be examined by many impartial testers before a claim should be made.

Argument from Adverse Consequences

Definition: Claiming that there must be ultimate justice to the universe, or else there would be total chaos.
Example: If there wasn't a god to punish the wicked, we would all be evil murderers and rapists right now.
Explanation: This is an obvious case of "Slippery Slope" fallacy. First of all, there is no proof that there is a cosmic justice. Secondly, there is no proof that if we didn't have it we would all be criminals.

Argument to Ignorance

Definition: Stating that something is true because it cannot be proven false or vice-versa.
Example: Of course there are angels, you can't prove that there aren't.
Explanation: This is a common logic fallacy in matters of faith. Something is only true if evidence validates it, not because there is lack of evidence to prove the contrary. If I closed my hand and told you a diamond materialized in it, but refused to show it to you, would you believe me just because you can't prove there isn't a diamond in my hand? Also called "argument from personal incredulity", "argument from incredulity", or "ad ignorantum".

Argumentum Ad Hominem

Definition: Refers to attacking a person making an argument, rather than the argument itself.
Example: Well of course you would make a stupid hypothesis like that, you never went to college.
Explanation: Often times in heated debates tempers rise, the people will attack each other's credentials, life style, education, etc. It doesn't matter if the person making the argument is rich or what school they went to, the only thing that matters is what their argument is. It is a very unprofessional, not to mention ignorant, to attack a person instead of their argument. Similar to "Poisoning the Well" where a person tries to discredit another before they begin their argument.

Circular Reasoning

Definition: Stating that an argument is true because another argument (that uses the first for validation) says it's true.
Example: God exists because the Bible says he does and the Bible is right because it was written by God.
Explanation: This is a commonly used fallacy when trying to argue in favor of religions. A claim can only be considered true if their is proof to support the claim. However, with this faulty reasoning, the claim itself is proof that the claim is true. Also known as "petitio principii", "begging the question", or "tautology".

Clustering Illusion

Definition: Assuming that because random events occur in clusters they aren't actually random.
Example: Cancer is ten times higher in this neighborhood than the surrounding ones, so there must be something wrong with that neighborhood.
Explanation: When examining small sections of random events clusters often can occur. This doesn't mean there is anything out of the ordinary. You must examine things on the whole before making an assumption. Depending on what's being tested, ten times higher isn't that much more than average.


Definition: Events that seem to be related in an unusual way or seem significant.
Example: Thinking about your friend, and then they call you on the phone or praying that you're sick realitive will get better and they do.
Explanation: There is a major difference between events being related or just a coincidence. When things are related they can be proven objectively. However, coincidences are totally subjective. Coincidences happen all the time, but it takes subjective validation to see them. Also, you can not leave out the law of truly large numbers. In order to find out the difference between true relations and coincidences all one needs to do is perform some properly organized tests.

Communal Reinforcement

Definition: When people in a community or group believe something because other people say it's true.
Example: A nurse at an emergency room says there are more accidents on a full moon, and tells her friends, who tell their friends and soon everyone believes it.
Explanation: This is often related to gossip and testimonial evidence. People tend to believe what the crowd believes. It is dangerous to believe what a group believes without first examining the evidence. In the case of the moon influencing the amount of accidents, the claim is false.

Confirmation Bias

Definition: Only looking for evidence that supports your hypothesis instead of looking for all types of evidence.
Example: A theologian looking for proof that a god exists, but not trying to find proof that the god doesn't exist.
Explanation: According to the scientific method, in order to prove something, you must try to prove it wrong. When you don't try to find evidence to the contrary of your claim you probably won't find any, which can give you very skewed results.


Definition: Faith is the belief in something regardless of evidence or proof.
Example: I believe in my god, there is no proof that he exists, but I believe in him through faith.
Explanation: Believing in something without proof is illogical. If I said that I have a Congressional Medal of Honor but didn't prove it, would you believe me? If you believe in things purely on faith, without proof, you have no way of knowing fact from fiction.

False Dilemma

Definition: Claiming that there are fewer sides to an issue than there really can be.
Example: You're either for or against gun control, so which is it?
Explanation: In this complex world there are very few issues that are truly black and white, but people will often try to make them seem that way because it forces you to pick between the choices that they want. This can give a very skewed appearance of what the issue is really about. Don't just trust someone to tell you all possible choices, you should try to find all possible choices yourself before deciding.

Gambler's Fallacy

Definition: Thinking that the past results affect a fixed random sequence.
Example: I've rolled a die twenty times and I haven't rolled a six yet, so there is a much higher chance of getting a six now.
Explanation: Provided the game is fair (meaning your not using loaded dice, or a fixed table, etc.) the odds of a game are fixed and do not change over time, regardless of past results. If a six hasn't shown up after twenty rolls the chances of getting a six are still one in six, this is a constant.

Guilt By Association

Definition: Thinking that an argument is false just because you don't like the type of people that endorse the argument.
Example: I refuse to believe any claim that an astrologer makes.
Explanation: This is a type of argumentum ad hominem in which a person immediately discounts a claim because he doesn't like the type of people who claim it. For a proper objective test, the type of people who make a claim should not be a factor as to whether the claim is valid or not.

Hasty Generalization

Definition: Making a generalization before you have gathered enough test data.
Example: In first test of fifty men, they preferred the color red over blue 60%, so obviously men prefer the color red.
Explanation: Generalizations are a dangerous stereotype to begin with, but this fallacy takes it even further by making the generalization before you even have a sampling of the majority of the test bed. You still have no idea what the rest of the results will be, so you shouldn't make a generalization yet.

Law of Truly Large Numbers

Definition: In a large enough sample many seemingly strange results can occur.
Example: It's not unlikely for heads to show up one hundred times in a row in a test of one billion flips.
Explanation: When working with very large numbers you can get all kinds of results that may seem odd, but are actually normal. This can cause many odd things to seem to occur, like finding hidden messages in books. The odds are rarely as high as are often claimed.

Nocebo Effect

Definition: An psychological result that causes a test, which normally works, to fail because the person "thinks" it won't work.
Example: A doctor gives a patient a pill to help their mild head ache, but tells them that it probably won't help them. Even though the pill was aspirin and would normally help, the patient continues to feel pain because they don't think the pill will help.
Explanation: A person's psychological outlook is very important when they are testing something. If they have a predisposition towards failure, they will often see a failure where one doesn't exist.

Optional Starting and Stopping

Definition: Starting or stopping a test whenever you want.
Example: A psychic trying to determine what is on the other side of a card will have a few warm-ups which they will sometimes include those results if they are right, but ignore them if they are wrong.
Explanation: It is important that the starting and stopping time of a test be set in advance and properly adjusted to best fit the test. Otherwise, the data can be very inaccurate because you can eliminate all failures at the beginning and end. Similar to "observational selection" where the observer picks which parts of the test will be used.


Definition: A type of illusion where a person "sees" something in a random background.
Example: People "seeing" the face of Jesus on the burnt areas of a tortilla shell.
Explanation: The human imagination can be very powerful, especially when we we're looking at a picture of random shapes. It becomes very easy to "see" many different objects.

Pious Fraud

Definition: Lying about something to try to prove something you feel is justified, good, or the right thing.
Example: A woman who has the wounds of the stigmata is later found to have made the wounds herself. When asked, she said she did it so that people would believe in God more.
Explanation: People will sometimes purposely lie about something so it can be shown as proof to a belief they feel very strongly about. This of course can result in altered test results.

Placebo Effect

Definition: A psychological result where a test that shouldn't work ends up working because the testers believe that it will work.
Example: Sugar pills are used instead of medicine, but seem to have the same positive effect on a patient.
Explanation: If you have a psychological predisposition towards success, your test results may show more success than usual because your in the state of mind to find success.

Positive-Outcome Bias

Definition: The tendency to publish positive outcomes over negative outcomes.
Example: While the FDA tests a new drug, the media only publishes the positive aspects of the FDA's findings.
Explanation: This is caused because people usually don't care about test results that fail. This causes the media to not bother with bad test results and only publish positive results. This can be a problem because people are often not informed of the negative aspects of a test.

Post Hoc Fallacy

Definition: Assuming because an event happened after another that the first event caused the second.
Example: You rip up a chain letter and the next day you lose your job.
Explanation: Things that seem related don't have to be. There are a lot of coincidences that seem connected, often times because you want them to be, that have nothing to do with each other. There must be proof that the second event was caused by the first, otherwise there is no reason to believe they are related. Also known as "ergo propter hoc".

Pragmatic Fallacy

Definition: Arguing that something is fact or true because it works, even though it hasn't been proven.
Example: I don't know how magnetic bracelets relieve pain, I just know that they do.
Explanation: Just because something appears to do something doesn't mean that it did. There is often an outside force that may have been the real cause. There are many other variables that could effect the outcome that may be ignored. For example, you may start wearing a magnetic bracelet for arthritis, and suddenly the pain in your hands is gone. However, even though you don't realize it, at the same time your job has changed equipment that is more ergonomically correct which is the real cause for your arthritis to go away.

Principle of Unnecessary Plurality

Definition: There is no need to create a new hypothesis when the existing one is accurate.
Example: Assuming that the moon effects your test scores, when the amount of time you study seems much more realistic.
Explanation: This is more commonly known as Occam's Razor. In most cases the more plausible solution is usually the correct one.

Red Herring

Definition: Entering a new argument into a debate to throw off the original debate.
Example: Your tax cut ideas may sound interesting, but what effect will they have on the ethics of abortion?
Explanation: This is often used in debates. It's basically a way to turn the current argument that a person is debating into a totally different argument. It's usually employed by someone who is losing an argument, they will throw in a red herring to switch the argument to something that they are better equipped to debate. This is essentially the same as changing the subject, but making it harder to notice. Also called "Smoke Screen" or "Wild Goose Chase".

Relativist Fallacy

Definition: Indicating that an argument doesn't apply to you, so therefore it is false.
Example: Many doctors are saying that smoking causes cancer, but I smoke and I don't have cancer, therefore the doctors are wrong.
Explanation: Just because something doesn't necessarily seem to apply to you, doesn't mean it's false. You may be part of a percentage that isn't affected, or it may affect you, and you just might not notice. Either way, your personal account is only one of many tests that must be done before something can be proven.

Regressive Fallacy

Definition: Assuming that change is caused by an external force, not the natural changes in the environment.
Example: Thinking the stock market is down because you lost your lucky rabbit's foot, when it normally fluctuates that amount.
Explanation: Most things in life fluctuate normally, and every so often they fluctuate larger amounts than what you're used to. This is normal in most things. The change must go far beyond what is normal in order to be considered part of an outside force.

Retrospective Falsification

Definition: Altering the content of a story each time it's told to better prove a point.
Example: The first time the story is told Bigfoot looked like a monkey. The second time Bigfoot was taller and hairier, etc.
Explanation: People tend to exaggerate certain parts of a story making it more interesting or they may confabulate (which is to fill in the blanks with something new). Eventually, a story can become totally different. Sometimes it's done unintentionally, other times it's done on purpose. It is very important to get your data first-hand to prevent this.

Selective Thinking

Definition: A person picks out favorable evidence and ignores unwanted evidence.
Example: Friday 13th is a bad day, so you end up looking for bad things to happen.
Explanation: If you're trying very hard to find evidence for something, even unlikely evidence seems to fit perfectly.


Definition: Believing something is true even though it is most likely or definitely false.
Example: A parent who doesn't want to believe their child stole from a store refuses to believe the store clerk, even though the evidence supports the clerk's claim.
Explanation: People don't like to believe that certain things can happen, and will often lie to themselves because the truth is so unwanted.

Self-Fulfilling Prophecy

Definition: When a belief you have is made reality because of something you do.
Example: A person's horoscope says they will have a bad day, so they don't even bother trying to enjoy their day. This causes them to have a bad day because they brought it upon themselves.
Explanation: People often will be the cause of predictions because they choose to, not because of prophecy forces them to. This can be prevented by doing a double-blind test.


Definition: Trying to force evidence into supporting a claim.
Example: Nostradomus mentioned a dark haired leader, so he must have been referring to Adolf Hitler.
Explanation: Just because evidence might fit the claim, doesn't mean that is does fit the claim. Claims must be exact in order to match, not just similar. Also called "extrapolation from general to the specific", see also Subjective Validation.

Slippery Slope

Definition: Arguing that something will happen, as a direct result to another claim, without offering proof that it will.
Example: If they ban smoking in public buildings the next thing they'll do is ban smoking all together.
Explanation: You can always make unfounded claims of what could happen if something is done, but unless you can offer proof that your claim will happen, your just like anybody else with an unfounded claim. Also called "reductio ad absurdum".

Spotlight Fallacy

Definition: Making judgments on a topic based upon what is popular of that topic.
Example: When the topic of Nevada comes up, most people think of gambling because Las Vegas is the most popular part of Nevada. However, the majority of Nevada has nothing to do with gambling.
Explanation: This is a common form of generalization often perpetuated by the media. People tend to only get information about the popular aspects of a topic.

Strawman Argument

Definition: A debate term where the arguer distorts or exaggerates another's claim to make it sound displeasing and unwanted.
Example: The senate did not pass the bill to reduce the state's alcohol limit while driving, therefore our senators are promoting drunk driving.
Explanation: It's very doubtful that the senators want to promote drunk driving. The arguer is trying to make the senators seem like terrible people by distorting their actions into something totally different.

Subjective Validation

Definition: Believing a vague description uniquely pertains to you, when it could pertain to everyone.
Example: Although you sometimes have bad tendencies, you are most often a good person.
Explanation: This often happens when people read their horoscope, have a tarot spread, or use other forms of divination. They feel that the vague terms apply to them. In order for a prediction to be properly valid it must be very precise. Vague descriptions apply to almost everyone. Similar to the "Forer Effect" or "Barnum Effect".

Sunk-Cost Fallacy

Definition: Continuing to support a lost cause because you don't want to be wrong about it.
Example: I've lost $500 dollars on lottery tickets, so I need to keep buying more so I can win my money back.
Explanation: If the cause seems hopeless it is usually better to stop and accept your losses, than to continue losing more. However, most people don't want to admit that they made the wrong decision, so they continue to support a cause that they know won't work, putting themselves in even more trouble.

Testimonial Evidence

Definition: A personal account told by someone which is used as evidence to support a hypothesis.
Example: Grandpa told me that when he was young he saw a unicorn while camping.
Explanation: Everyone has a story, and often times these stories can be wrong. Don't believe everything you're told. It is important to do research yourself. People lie, make stuff up, and forget details.

Tu Quoque

Definition: Justifying ones own mistakes by saying that others have them as well.
Example: My creationism theory might not be rock solid, but your evolution theory isn't either.
Explanation: Just because another theory isn't very good doesn't make yours any better.

Wishful Thinking

Definition: The unintentional act of misinterpreting data to support your claim.
Example: A recent test on crop circles turned up inconclusive, which is proof that aliens exist.
Explanation: If you really want the evidence to prove your theory, you may believe that it does, even if the results turn out not to support your claim.

www.skepdic.com - The Skeptic's Dictionary.
www.theness.com - New England Skeptic's Society.
www.nizkor.org/features/fallacies - The Nizkor Project Fallacies.
www.randi.org - The James Randi Educational Foundation.