There is a great deal of critical thinking concepts that can be both convenient to use and help improve our critical thinking skills. However, some critical thinking concepts should be considered to be indispensable to being a human being because it’s a requirement of having a minimal capacity to reason and argue properly. The list of critical thinking terminology listed here are used to refer to concepts that everyone should know about—and yet many people either haven’t been informed about them or they don’t understand them properly:
ad hominem – A Latin phrase that literally means “to the person.” It refers to insults and usually to fallacious forms of reasoning that make use of insults or disparaging remarks. For example, we could respond to the a doctor’s claim that “smoking is unhealthy” by saying the doctor who made the argument drinks too much alcohol.
anecdotal evidence – To attempt to persuade people to agree to a conclusion based on the experiences of an individual or even many individuals. Anecdotal evidence is often a fallacious type of argumentation. For example, many individuals could have experiences of winning sports games while wearing a four-leaf clover, but that doesn’t prove that four-leaf clovers actually give sports players luck. No fallacy is committed when the experiences of people are sufficient to give evidence for a causal relation and mere correlation can be ruled out. Fallacious appeals to anecdotal evidence could be considered to be a form of the “hasty generalization” fallacy. Also relevant is the “cum hoc ergo propter hoc” fallacy.
appeal to authority – (1) An argument that gives evidence for a belief by referencing expert opinion. Appeals to authority are not fallacious as long as it actually appeals to the unanimous opinion of experts of the relevant kind. (2) A fallacious argument that appeals to the supposed expert opinion of others when the opinion referred to is not unanimous or uncontroversial among the experts or when the supposed expert that is appealed to is not an expert of the relevant kind.
appeal to ignorance – A fallacious argument that concludes something on the basis of what we don’t know. For example, to claim that “we should agree that extraterrestrials don’t exist because we can’t yet prove they exist” is fallacious because there are other reasons we might expect extraterrestrials to exist, such as the vastness of the universe.
argument – (1) To provide statements and evidence in an attempt to lead to the plausibility of a particular conclusion. For example, “Punching people is generally wrong because hurting people is generally wrong” is an argument. (2) A verbal battle. (3) The discussion that concerns a disagreement.
begging the question– A logical fallacy that is used by an argument that uses a premise to prove a conclusion when a controversial premise trivially implies that the conclusion is true. For example, “The death penalty is murder, so the death penalty is wrong” requires a controversial premise (that the death penalty is murder) to prove something else controversial (that the death penalty is wrong). “Begging the question” is similar to “circular reasoning.”
charity – (1) The virtue in a disagreement or debate to describe other people’s beliefs and arguments accurately rather than to misrepresent them as being less reasonable than they really are. If we are not charitable in this way, then we will create a fallacious “straw man” argument. (2) The virtue concerned with helping others who are in need. For example, giving money to the poor is often charitable in this sense. (3) An organization or institution that exists to try to help others who are in need.
circular argument – An argument with a premise that’s identical to the conclusion. For example, “All dogs are animals because all dogs are animals.” The logical form of a circular argument is “a; therefore a.” Circular arguments are similar to the “begging the question” fallacy. Also see “circular reasoning.”
circular reasoning – (1) Reasoning involving the justification of beliefs that require us to accept other beliefs that aren’t justified unless we assume the belief that we want to justify in the first place. A simple form of circular reasoning is the following: A is justified because B is justified; B is justified because C is justified; and C is justified because A is justified. For example, “We should agree that stealing is wrong because it should be illegal; we should agree that stealing should be illegal because we shouldn’t want people stealing from us; and we shouldn’t want people stealing from us because it’s wrong.” (2) A “circular argument.”
conclusion – A statement that is meant to be proven or made plausible in consideration of other statements. “Conclusions” are often contrasted with “premises.”
continuum fallacy – A fallacy that is committed by an argument that appeals to the vagueness of a term to unreasonably conclude something (perhaps based on the fact that we can’t draw the line). For example, we might not know where to draw the line concerning how many hairs can be on a person’s head before that person is no longer bald, but we would commit the continuum fallacy to conclude from that fact that no one is bald.
contradiction – When two propositions cannot both be true due to their logical form. “Socrates was a man” and “Socrates was not a man” are two statements that can’t both be true because the logical form is “a” and “not-a.” (“a” is any proposition.)
counterexample – (1) An object or state of affairs that disproves a belief. For example, a white raven disproves the belief that “all ravens are black.” (2) An argument meant to prove another argument to be logically invalid by using the same argument form as the other argument, but the counterargument must have obviously true premises and an obviously false conclusion. Consider the invalid argument, “If dogs are lizards, then dogs are reptiles. Dogs are not lizards. Therefore, dogs are not reptiles.” A counterexample would be, “If dogs are reptiles, then dogs are animals. Dogs are not reptiles. Therefore, dogs are not animals.”
criticism – (1) An argument that is meant to persuade us to reject a belief of another argument. See “objection.” (2) Disparaging remarks, fault-finding, or judging something as falling short of certain requirements or standards.
cum hoc ergo propter hoc – Latin for “with this, therefore because of this.” A logical fallacy committed when an argument concludes that something causes something else to happen due to a correlation. For example, the fact that a person takes a sugar pill before recovering from an illness doesn’t prove that she recovered from the sugar pill. She might have recovered for some other reason. This fallacy is a version of the “false cause” fallacy.
debate – A prolonged discussion concerning a disagreement that is characterized by two or more sides that (a) try to give reasons to believe differing incompatible conclusions, (b) try to explain why the conclusions of the opposing side should be rejected, and (c) try to explain why the arguments given by the opposing side should be rejected. Debates need not be between two people and they need not exist in a face-to-face presentation. A single philosophical essay can be considered to be part of a debate that’s been going on for hundreds or thousands of years by philosophers in different time periods reading various arguments and responding to them.
deduction – Reasoning or argumentation characterized by the fact that the truth of the premises are meant to guarantee the truth of the conclusion. For example, “All men are mortal. Socrates is a man. Therefore, Socrates is a mortal.” Deduction is often contrasted with “induction.”
epistemic certainty – The degree of justified confidence we have in our beliefs. To be certain that something is true could mean (a) that we have a maximal degree of justification for that belief, (b) that we can’t doubt that it’s true, or (c) that it’s impossible for the belief to be false. To be absolutely certain that something is true is to have no chance of being wrong. For example, we are plausibly absolutely certain that “1+1=2.”
fact – A state of affairs, relation, or part of reality that makes a statement true. For example, it’s true that objects fall and will continue to fall because it’s a fact that “the law of gravity exists” or accurately describes relations that exist in reality.
fallacy – An error in reasoning. Formal fallacies are committed by invalid arguments and informal fallacies are committed by errors in reasoning of some other kind.
false dilemma – A fallacious argument that requires us to accept fewer possibilities than there plausibly are. For example, we could argue the following—“All animals are mammals or lizards; sharks are not mammals; therefore, sharks are lizards.” False dilemmas are related to the “one-sidedness” fallacy.
hasty generalization – A fallacious argument that concludes something because of insufficient evidence. Hasty generalizations conclude that something is true based on various observations when the observations are not actually a sufficient reason to believe the conclusion is true. For example, to conclude that all birds use their wings to fly based on seeing crows and swans would be a hasty generalization. Not all generalizations are fallacious. See “induction” for more information.
induction – To generalize based on a sample. For example, the view that the future will resemble the past in order to arrive at conclusions. To see only white swans could lead to the conclusion that all swans are white. To see that bread has always been nutritious could lead to the conclusion that similar bread will still be nutritious tomorrow. Induction is often contrasted with “deduction.” Not all inductive reasoning is well-reasoned. See “hasty generalization” for more information.
invalid – (1) An argument form that can have true premises and a false conclusion at the same time. An example of an invalid argument is the following—“Socrates is either a man or a mortal. Socrates is a man. Therefore, Socrates is not a mortal.” “Invalid” is often contrasted with “valid.” See “logical form” for more information. (2) Unreasonable. (3) Inappropriate or failing to meet specified requirements. (4) Someone who is chronically ill.
Justification – (1) Evidence or reasons to believe something. Observation is one of the strongest forms of justification; but self-evidence, intuition, and appeals to authority could also be legitimate forms of justification. For example, people can justify their belief that they can feel pain by having actual pain experiences. (2) The supporting premises of an argument.
justified belief – Some philosophers believe that justified beliefs are those that are given a sufficiently good justification, but it is possible that justified beliefs are defensible beliefs that one has no sufficient reason to reject. For example, a typical uncontroversial example of a justified belief is the belief that “1+1=2” but few to no people know how to properly justify this belief using argumentation.
knowledge – Classically defined as “justified true belief,” but many argue that it must be “justified in the right way” or that there might be a fourth factor. An eyewitness who sees a murderer commit the act knows who the murderer is because the belief is justified through observation and the belief is true. However, consider a situation where Sally believes that cows are on the hillside because she mistakes cardboard cutouts of cows as the real thing, and some real cows are on the hillside hiding behind some trees. The belief is justified and true, but some philosophers argue that Sally doesn’t actually know that cows are on the hillside.
logical form – The logical form of an argument consists in the truth claims devoid of content. “The sky is blue or red” has the same logical form as “the act of murder is right or wrong.” In both cases we have the form, “a or b.” (“a” and “b” are statements.) In this case the truth claim is that one thing is true and/or another thing is true.
nonrational persuasion – Fallacious and manipulative forms of persuasion. Nonrational persuasion does not always take the form of an argument, and it often appeals to our biases. For example, the news could continually have stories about how our enemies harm innocent people to give us the impression that our enemies are evil. This is similar to the “one-sidedness fallacy,” but no actual argument needs to be presented. People are likely to jump to conclusions on their own.
one-sidedness: (1) A fallacy committed by an argument that present reasons to believe something while ignoring or marginalizing the reasons against believing it. For example, a person selling a vacuum cleaner could tell us how it can pick metal objects off the floor, but decide not to mention that it tends to break after being used a few times. “One-sidedness” is also known as “selective evidence” and highly related to “cherry picking” and “quoting out of context.” (2) To be incapable or unwilling to see things from more than one reasonable point of view.
philosophy – (1) Literally means “love of wisdom.” The quest to attain knowledge and improve ourselves. It generally refers to various domains of study that involve systematic attempts to greater understanding while attempting to be reasonable other than those domains that have been designated to mathematicians or scientists. Arguments and theories concerning the proper domain of philosophy is known as meta-philosophy. (2) Opinions regarding what’s important in life or how one should conduct oneself. (3) A declaration of principles, values, or goals of an institution.
psychological certainty – The feeling of some degree of confidence about a belief. To be psychologically certain that something is true is to feel highly confident that it’s true. For example, a person might feel absolutely confident that trees really exist and later find out that our entire world takes place within a dream.
proposition – A truth claim or the conceptual meaning behind an assertion. The statement “Socrates is a man and he is mortal” contains two propositions. (a) Socrates is a man and (b) Socrates is mortal. Propositions are not statements because there can be multiple statements that refer to the same proposition. For example, there are many languages that offer us different ways to say, “Socrates is a man and he is mortal.”
red herring – A fallacious kind of argument that is meant to distract people from arguments and questions made by the opposing side. These kinds of arguments are meant to derail the conversation or change the subject. For example, a politician might be asked if we should end our wars, and she might reply, “What’s really important right now is that we improve the economy and create jobs. We should do that by lowering taxes.”
reductio ad absurdum – Latin for “reduction to the absurd.” Also known as the “argument from absurdity.” It’s a form of argument that justifies why an argument or claim should be rejected insofar as it would have absurd consequences. For example, consider the following argument—“Stars exist; the Sun is a star; therefore Stars don’t exist.” This argument leads to an absurd consequence in the form of a logical contradiction (i.e. that something exists and doesn’t exist.)
slippery slope – (1) An argument that requires us to believe that incremental causal changes will likely happen given that we make certain decisions. For example, having violence on television might desensitize people to violence and lead to even greater violence on television in the future by an ever-increasing demand for more thrilling forms of entertainment. (2) An informal fallacy committed by arguments that require us to believe that some decision will likely lead to incremental changes for the worse without sufficient evidence for us to accept that the changes are likely to actually happen. For example, some people argue that we shouldn’t legalize same-sex marriage because that would likely lead to marriages between brothers and sisters, and eventually it would lead to marriages between humans and nonhuman animals.
sound argument – An argument that’s valid and has true premises. For example, consider the following sound argument—“If all dogs are mammals, then all dogs are animals. All dogs are mammals. Therefore, all dogs are animals.”
statement – Classically defied as a sentence that’s true or false. However, some philosophers argue that a statement could have some other truth value, such as neither true nor false. For example, “This sentence is false” might be neither true nor false.
straw man – A fallacious form of reasoning consisting of misrepresenting another person’s arguments or beliefs in order to convince people that the arguments or beliefs are less reasonable than they really are. For example, Andrea might claim that “stealing is generally wrong,” and Charles might then reply, “No. Andrea wants us to believe that stealing is always wrong, but sometimes stealing might be necessary for survival.” The opposite of straw man is being charitable to another person’s arguments and beliefs—to present them as rationally defensible as they really are.
true – The property that propositions have that makes them based on reality. According to Aristotle, a statement is true if it corresponds with reality. For example, “Socrates was a man” is true. However, there might be other uses of the word true, such as, “The pawn can move two spaces forward when it is first moved in a game of Chess.” Many such “truths” are based on agreements or human constructions and are not factual in the usual sense of the word. “True” is often contrasted with “false.”
valid – An argument is valid when it has a logical form that assures us that true premises guarantee the truth of the conclusion. It is impossible for a valid argument to have true premises and a false conclusion at the same time. For example, consider the following valid argument—“If Socrates is a dog, then Socrates is a mammal. Socrates is a dog. Therefore, Socrates is a mammal.” “Valid” is the opposite of “invalid.” See “logical form” for more information.