Critical Thinking Glossary

The Critical Thinking (CT) Glossary is a curated list of standardized terms describing the ideas comprising each of the four elements of critical thinking: concepts, skills, ethics, and impediments. By creating a standard language of CT, the elements of CT can be reinforced across contexts and learning can be transferred across subjects.

Our glossary is in its development phase and we invite visitors to add new entries and enhance existing ones. CT Foundry curates this glossary and will modify contributions as necessary to ensure accurate, standardized, and non-redundant entries.

Format of Entries
Entries in the CT glossary should be organized into the following sections. See existing entries for examples of proper formatting.

Term
Required. Generally one to three words at the sub-heading 1 level.

The standard term to be used to label the concept, skill, ethic, or impediment being described. This term is intended to be used across contexts and subject areas and so must be both descriptive and general enough to apply across domains. The term for any given entry may change over time as better terminology is identified. Terms should be placed alphabetically within their respective group (concept, skill, ethic, or impediment).

Definition
Required. Plain English at the paragraph level. Should follow on next line after Term.

All entries should include a simple, concise, and accurate definition. Examples illustrating the term being defined are always helpful.

Synonyms
When applicable. Comma-separated list at the sub-heading 2 level, starting with "Synonyms: ".

As part of our goal to establish a standard set of terms, we wish to avoid redundant entries in the CT Glossary. Therefore, when there is more than one term for a given entry, alternative terms should be listed as synonyms. For example, while "Prevalence" is another way to describe "Base Rate", we have an entry only for "Base Rate" and specify "Prevalence" as a synonym.

Concepts
Good critical thinking requires understanding certain concepts. Some can be simple, others complex.

Absolute Risk
The chances that something will occur in a given group. For example, the chances of being struck by lightning in the United States in a given year is 1 in 700,000. Compare to relative risk, which compares the chances that something will occur in one group relative to another group. For example, the relative risk of lightning strike for males is about three times greater than the risk for females, but it is still very low in terms of absolute risk.

Base Rate
The frequency that something occurs or is true within a given group. For example, about 14% of all people in the US have a first name that begins with "A", meaning that the base rate of names that begin with "A" in the US at this time is 14%, or about one in every seven people.

Claim
Saying that something is true. Claims can be divided into subjective and objective.

Critical Thinking
The act of determining how likely an objective claim is to be true.

Direct Evidence
Any fact about a claim. For example, seeing rain fall from the sky this morning as evidence for the claim that it rained this morning. All other things being equal, direct evidence is stronger than indirect evidence.

Evidence
Any fact or facts used to decide if an objective claim is true. The strength of evidence can determined by classifying it into one or more categories, including physical evidence, remembered evidence, direct evidence, indirect evidence, first-hand evidence, second-hand evidence, recorded evidence, replicated evidence, planned evidence, unplanned evidence, and random sample. Sample size is also a factor in determining the strength of evidence.

Synonyms: Facts
==== See Also: Objective Claim, Physical Evidence, Remembered Evidence, Direct Evidence, Indirect Evidence, First-Hand Evidence, Second-Hand Evidence, Recorded Evidence, Replicated Evidence, Planned Evidence, Unplanned Evidence, Random Sample, Sample Size ====

Fact
Anything that is true for everyone.

First-Hand Evidence
A fact that was seen, touched, smelt, felt, or heard by the person who is reporting it. For example, using the fact that you watched the moon go in front of the sun as evidence for the claim that there was a solar eclipse. All other things being equal, first-hand evidence is stronger than second-hand evidence.

Indirect Evidence
Any fact related to the claim, but not about the claim itself. For example, using the fact that the sidewalk is wet as evidence for the claim that it rained this morning. All other things being equal, indirect evidence is weaker than direct evidence.

Objective Claim
A claim that must be either true for everyone or false for everyone. A claim that something is a fact. For example, saying that the the Earth is flat is an objective claim because it must be either true for everyone or false for everyone. It cannot be true for some people and false for others. All objective claims can be evaluated as either probably true, probably false, or not enough information to say.

Physical Evidence
A fact that can be seen, felt, heard, smelt, or tasted, either directly or by using instruments.

Planned Evidence
Evidence gathered using a method that is planned out ahead of time. For example, you gather evidence on the existence of Bigfoot by deciding to ask each of your teachers tomorrow to write down their answer to the question "Is Bigfoot real?". The best planned evidence uses a sound method that leads to physical or recorded evidence. Planned evidence is more likely to be accurate than unplanned evidence. Also, planned evidence can be used to obtain replicated evidence.

Random Sample
A sample that is chosen in a way that there is an equal chance that any part of the thing being sampled is picked. Random samples are more likely to accurately tell us what the whole is like than are non-random samples.

Relative Risk
The chances of something occurring in one group compared to another. For example, if color-blindness occurs in eight percent of all men and one-half of a percent in all women, then the relative risk of men having color-blindness compared to women is 1,600 percent. In other words, men are 16 times more likely to be color blind than women.

Recorded Evidence
A fact that is recorded in some way, such as a written description, a picture, a video, or an audio recording. Recorded evidence is a form of physical evidence because it can be seen or heard.

Refuting Evidence
Evidence that contradicts a claim. For example, if I claim that all swans are white and you show me a black swan, that is refuting evidence for my claim.

Remembered Evidence
A fact recalled from memory. Remembered evidence has many problems due to the unreliability of memory. Here is an overview of the different types of memory errors.

Replicated Evidence
A fact has already been observed at least once before in other circumstances. Replicated evidence is a kind of supporting evidence. The more times a fact is observed, the more likely it is to be true. For example, if you measure the height of your dog as 22 inches and your friend also measures the height of your dog at 22 inches, your friend's measurement is replicated evidence and this evidence increases the likelihood that your dog is really 22 inches tall. If, on the other hand, your friend measures the height of your dog as 21 inches, that is refuting evidence and it decreases the likelihood that your dog is really 22 inches tall.

Sample
A small part of something that is supposed to show what the whole thing is like.

Sample Size
The number of items in a sample. The larger the sample size, the more confident we can be that the sample resembles the whole thing that it came from.

Second-Hand Evidence
A fact that was seen, touched, smelt, felt, or heard by someone other than the person reporting it. For example, using the fact that your friend told you they watched the moon go in front of the sun as evidence that there was a solar eclipse. All other things being equal, second-hand evidence is weaker than first-hand evidence.

Sound Method
A method can be more or less sound, depending on how much of each of the following characteristics:


 * Clear (easily understood)
 * Concise (no extra steps, no steps left out)
 * Repeatable (can be performed by other people at other times)
 * Recorded (written down or captured via audio or video so that doing it does not rely on memory)
 * Complete (works for all cases).

Subjective Claim
A claim that can be true for some people and false for others at the same time. For example, "Cats are better than dogs" is a subjective claim because it can be both true for some people and false for other people at the same time.

Supporting Evidence
Evidence that supports a claim. For example, if I claim that Ougadougou is the capital city of the country Burkina Faso, a map showing Ougadougou as the capital of Burkina Faso would be supporting evidence of my claim.

Unplanned Evidence
Evidence that is gathered in an unplanned way. For example, your friend mention to you that Bigfoot is real. This is unplanned evidence for the existence of Bigfoot. Unplanned evidence is less likely to be accurate than planned evidence.

Skills
Skills are the abilities required for good critical thinking. With sufficient practice, skills can become habits.

Ethics
Good critical thinking also involves adopting certain ethics.

Impediments
We all experience impediments to critical thinking. Recognizing and compensating for these impediments is key to good critical thinking.

Ad Hominem Argument
A logical error where a claim is refuted based on some real or perceived motive or characteristic of the person making the argument. Motives and characteristics of arguers do not make their claims any more or less true, only evidence does. For example, if a neighbor claims that allowing dogs in the local park is killing the trees, saying that their claim is false because they hate dogs, even if they do hate dogs, is an ad hominem argument that doesn't make their claim about dying trees any more or less true. Ad hominem arguments should be avoided.

Appeal to Hypocrisy
A logical error where a claim of wrongdoing is refuted based on the fact that others have done the same thing. For example, arguing that it is OK to steal because others have stolen as well is an appeal to hypocrisy that doesn't make the claim any more true or false. If someone has done something wrong, the fact that someone else has also done wrong does not excuse the behavior. Appeals to hypocrisy should be avoided.

Argument from Authority
A claim that something is true just because a person, book, or other source of information claims it is true. Arguments from authority are weak support for a claim unless what the authority says is in turn based on good evidence and reasoning. Arguments from authority should be replaced with arguments from evidence.

Argument from Faith
A claim that something is true because one sincerely believes it to be true, independent of evidence. Arguments from faith should be avoided.

Argument from Ignorance
A logical error where a claim is argued to be true because it has not yet been proven false. One can make a claim about anything that has not yet been proven false, like "There is life on the planet Saturn", but being able to make a claim that has not or cannot be proven false does not tell us anything about how likely it is to be true. Arguments from ignorance should be avoided.

Argument from Memory
A claim that something is true based on remembered evidence. An argument from memory is one type of an argument from evidence, but it is weak because remembered evidence is often unreliable. It is better to use arguments from evidence that are based on recorded evidence or physical evidence.

Base Rate Fallacy
Forgetting to consider the base rate of a given event or characteristic when considering its probability in a given instance. This error can lead to false conclusions. For example, if I guessed that you had a close family member whose first name began with an "A" or a "J" (which is true for about 25% of the US population), thinking that it was an extremely lucky guess, or that I had special powers, would be an example of the base rate fallacy. Alternatively, if a positive test result for a disease is correct 95% of the time, but the disease only occurs in 1 out of every 1,000 people, it would be a base rate fallacy to conclude that a person with a positive test result is likely to have the disease since, because of the disease's low base rate, a positive result still means that there is less than a 2% chance the person actually has the disease.

Causation Fallacy
Thinking that A causes B because A happens before or together with B. For example, thinking that a rooster crowing every morning causes the sun to rise. The best way to actually establish that A causes B is through an experiment.

Confirmation Bias
Looking for or remembering only the evidence that supports a claim and not looking for or remembering the evidence the refutes it. For example, you remember looking at a clock a number of times recently and seeing 10:12 each time, which is your birthday. You therefore conclude there is something special going on when really, you just forgot all the times you looked at the clock and saw something other than 10:12. Here is an excellent interactive demonstration of confirmation bias.

Conspiracy Fallacy
Thinking that the reason there is a lack of evidence for a claim is because there is a conspiracy to cover it up.

False Equivalence
Treating the evidence for a claim as equal to evidence against it, or vice versa, even though it is not. For example, claiming that because some people hold that the Earth is at the center of the solar system, we cannot say it is probably true that the sun is actually at the center.

Illusion
A distortion of sight, hearing, touch, smell, or taste. Illusions are common and can often lead to misinterpreting evidence and coming to incorrect conclusions. Here is an example of a convincing optical illusion. Seeing patterns, such as faces, in objects where there is no actual pattern is a particular form of illusion can pareidolia. Click here for more information on pareidolia. People can be primed to experience illusions as well. Here is an example of a primed auditory illusion called the McGurk Effect. Problems caused by illusions can be overcome by using instruments to gather evidence, such as measuring how light or dark something is using a photometer instead of your eyes.

Lottery Fallacy
Mistakenly thinking that because something is unlikely to happen to a single person or in a single instance it is unlikely to happen among multiple people or multiple instances. For example, while it is unlikely after any given dream about someone you know that they will call you next day, if you have enough dreams about people you know, it's likely that at some point, the person you just dreamt about will call you. This is called the lottery fallacy because even though the chances of any one person winning the lottery is tiny, the chances that someone will win the lottery are large.

Straw Man Argument
Arguing that a claim is false by refuting a different claim while pretending it is the original claim. The straw man claim is usually easier to refute than the real claim. For example, refuting a claim that increasing property taxes will help the community by arguing that everyone will end up paying more in taxes. This is a straw man argument because it switches a claim about a tax on property owners with a claim about a tax on everyone. Straw man arguments violate the ethic of of intellectual honesty and intellectual charity.