Critical Thinking and Logical Reasoning

Introduction

Critical Thinking and Logical Reasoning helps you examine claims, evidence, assumptions, and conclusions instead of accepting ideas automatically. In Grades 9–10, these skills support stronger reading, writing, discussion, research, problem-solving, and decision-making across subjects. Critical thinking is not the same as being negative or argumentative. It means asking fair questions, checking reasons, looking for relevant evidence, considering alternatives, and being willing to revise a judgment when better information appears.

In this course, you will learn how arguments are built, how deductive and inductive reasoning differ, how to test the quality of evidence, how common fallacies and cognitive biases can distort judgment, and how to communicate conclusions responsibly. You will also practice applying these skills to schoolwork, media, everyday choices, and digital information.

The diagram above connects critical thinking with skills such as analyzing, reasoning, and problem-solving. As you work through the course, notice how these skills often operate together rather than separately.

The TED-Ed video above introduces a practical process for making better decisions. While watching, identify which steps could help you slow down before accepting a first impression.

What Critical Thinking Involves

Critical thinking is the careful analysis and evaluation of facts, observations, evidence, and arguments in order to form a justified judgment. A strong critical thinker does not simply ask, “Do I agree?” Instead, you ask questions such as: What exactly is being claimed? What reasons support it? What evidence is relevant? What assumptions are hidden? What other explanations are possible? What would change my mind?

Critical thinking includes both skills and habits. The skills include interpreting information, comparing reasons, identifying relationships, drawing inferences, and evaluating evidence. The habits include curiosity, intellectual humility, fairness, patience, and a willingness to correct errors.

Claims, Reasons, and Arguments

An argument is a set of statements in which one or more statements are offered as reasons for accepting another statement. The supporting statements are called premises. The statement being supported is the conclusion.

For example:

Premise: The school library is open after classes today.

Premise: You need a reliable source for your history project.

Conclusion: You have a useful opportunity to research at the school library today.

This argument does not guarantee that the library is the only good place to research. It simply provides a reasoned connection between information and a practical conclusion. In real discussions, arguments may be more complex, and some premises may be unstated.

An argument map makes the structure of reasoning visible. It can show a main claim, supporting reasons, objections, and responses. Mapping is useful because it separates the quality of a person's reasoning from the person's identity or popularity.

Assumptions and Hidden Premises

An assumption is something taken for granted within a line of reasoning. Some assumptions are harmless and reasonable; others need examination.

Consider the claim: “We should move the class discussion online because everyone will participate more.”

A hidden assumption is that an online format will increase participation for all students. You can test that assumption by asking about access, comfort with technology, previous participation data, and alternative formats. Critical thinking often begins when you make hidden assumptions visible.

Deductive, Inductive, and Abductive Reasoning

Different kinds of reasoning offer different levels of support for conclusions. It is important to judge an argument by the standards appropriate to its type.

Deductive Reasoning

Deductive reasoning aims at certainty. A deductive argument is valid when it is impossible for all of its premises to be true while its conclusion is false. A deductive argument is sound when it is valid and its premises are in fact true.

A classic example is:

Premise: All mammals are warm-blooded.

Premise: Dolphins are mammals.

Conclusion: Dolphins are warm-blooded.

If both premises are true, the conclusion must be true. Notice that validity concerns the logical connection between premises and conclusion. Soundness adds a second requirement: the premises must actually be true.

The Venn-style diagram above illustrates a traditional syllogistic form. Visual models can help you test whether a conclusion follows from the relationships stated in the premises.

The Crash Course video above explains philosophical argumentation and deductive reasoning. As you watch, distinguish between whether an argument is valid and whether its premises are believable.

Inductive Reasoning

Inductive reasoning moves from observations or examples toward a broader conclusion. Its premises support a conclusion as probable rather than guaranteed. A strong inductive argument gives good reason to expect the conclusion to be true, but new evidence could still change the judgment.

Example:

Premise: In five separate measurements this week, the school garden soil was dry by late afternoon.

Conclusion: The garden will probably need watering in the late afternoon on similar dry days.

This conclusion is reasonable but not certain. Rain, shade, temperature, or a change in irrigation could affect the result. Good inductive reasoning depends on the quality, amount, and representativeness of evidence.

Abductive Reasoning

Abductive reasoning looks for the best available explanation of an observation. It is common in science, diagnosis, troubleshooting, and everyday problem-solving.

Observation: A classroom projector suddenly shuts down.

Possible explanations: the power failed, the cable is loose, the device overheated, or the battery backup ended.

An abductive thinker compares explanations against the evidence and prefers the one that best fits the facts while remaining open to revision.

This Crash Course video explores induction, abduction, counterarguments, and questioning. Pause after an example and ask what extra evidence would make the conclusion stronger.

Testing Arguments

A strong argument requires more than a confident conclusion. You need to examine both the truth or credibility of the premises and the quality of the connection between premises and conclusion.

Relevance, Sufficiency, and Acceptability

A useful checklist for argument evaluation asks whether reasons are:

Relevant: Do the reasons actually bear on the conclusion?
Sufficient: Is there enough support for the strength of the claim?
Acceptable: Are the premises trustworthy, accurate, or well-supported?

Suppose someone claims, “Our school should start later because my favorite athlete wakes up late.” The reason may be true, but it is not relevant evidence about school schedules. A better argument might use research about adolescent sleep, transportation constraints, and academic scheduling.

Counterexamples and Alternative Explanations

A counterexample is a case that shows a general claim is false or that a reasoning pattern does not work. If someone says, “All successful people wake up before 5 a.m.,” one verified successful person who does not follow that routine is enough to disprove the universal claim.

An alternative explanation is a different cause or interpretation that could also fit the evidence. If students' test scores rise after a new study app is introduced, the app may have helped, but perhaps the class also received extra tutoring or the second test was easier. Critical thinkers look for competing explanations before claiming causation.

Logical Fallacies

A logical fallacy is a flaw in reasoning. A fallacious argument can still have a true conclusion, but the reasoning does not adequately establish that conclusion. Recognizing fallacies should help you improve arguments, not simply label or dismiss people.

The diagram above illustrates how apparently plausible statements can fail to justify a conclusion. A visual overlap does not automatically prove the relationship a speaker claims.

Common Fallacies to Recognize

Ad hominem attacks the person instead of addressing the person's argument. “Your recycling proposal is wrong because you are messy” does not evaluate the proposal itself.

Straw man misrepresents a position so that it is easier to attack. If one student proposes reducing homework on weekends and another replies, “So you want students never to study,” the reply exaggerates the original claim.

False dilemma presents only two choices when more options exist. “Either we ban phones completely or nobody will learn” ignores possible middle positions such as limited use during specific activities.

Hasty generalization draws a broad conclusion from too little or unrepresentative evidence. Meeting two rude tourists does not justify a claim about all tourists from their country.

Appeal to popularity treats popularity as proof. Many people believing a claim does not by itself make the claim true.

Post hoc reasoning assumes that because one event happened after another, the first event caused the second. Sequence alone does not establish causation.

Circular reasoning uses the conclusion as part of its own support. “This rule is fair because it is a fair rule” gives no independent reason.

An argument map can help you locate the exact step where reasoning breaks down. When analyzing a fallacy, identify the specific premise-to-conclusion connection that fails.

Cognitive Biases and Metacognition

A cognitive bias is a systematic tendency in judgment that can influence how people notice, remember, or evaluate information. Biases are not proof that a person is irrational in every situation. They are patterns that can make certain errors more likely.

The Cognitive Bias Codex groups many named biases. You do not need to memorize them all. For Grades 9–10, it is more useful to understand a few common patterns and learn strategies for checking your own thinking.

Confirmation Bias

Confirmation bias is the tendency to seek, notice, interpret, or remember information in ways that support an existing belief. If you believe a study method is excellent, you may remember the times it worked and overlook times it did not.

A practical defense is to ask, “What evidence would count against my view?” Then actively search for that evidence.

Anchoring and First Impressions

Anchoring occurs when an initial number, claim, or impression influences later judgment more than it should. A first price in a negotiation, a first headline, or a first estimate can become a mental reference point.

You can reduce anchoring by generating an independent estimate before looking at other people's numbers and by comparing several sources.

Availability and Vividness

The availability heuristic can make events seem more common or probable when examples come to mind easily. Dramatic or recent stories may feel more representative than they really are.

To check this tendency, compare memorable examples with broader data. A vivid anecdote can be useful, but it is not automatically representative evidence.

Metacognition: Thinking About Your Thinking

Metacognition means monitoring and reflecting on your own thinking. You can ask: Why do I believe this? How confident am I? What assumptions am I making? What evidence have I ignored? Am I treating a preferred conclusion differently from a disliked one?

Strong critical thinking is not a search for perfect certainty. It is a disciplined effort to improve the quality of judgment.

Evaluating Evidence and Sources

Good reasoning depends on good evidence. A useful source is not simply one that agrees with you. You should consider authorship, expertise, evidence, context, date, purpose, and whether independent sources support the same claim.

This Crash Course video focuses on evaluating evidence in digital environments. Notice the difference between a source that merely mentions a claim and evidence that actually supports it.

Questions for Source Evaluation

When you encounter an article, post, video, chart, or AI-generated answer, ask:

Source: Who created it, and what relevant expertise or direct access do they have?
Evidence: What data, documents, observations, or sources support the claim?
Context: Is important information missing, cropped, edited, or taken out of context?
Corroboration: Do independent reliable sources support the same key facts?
Purpose: Is the goal to inform, persuade, entertain, sell, provoke, or mislead?

A single weak source does not become strong evidence because it is repeated many times. Trace important claims back to original or high-quality sources when possible.

This newer Crash Course video demonstrates source checking and fact-checking strategies. Use it to compare quick verification methods with more careful research for high-stakes claims.

Language, Framing, and Persuasion

Critical reasoning is closely connected to English language arts because word choice affects how claims are interpreted. Two sentences may describe the same event with different emotional framing. “Only 60 percent succeeded” and “A majority of 60 percent succeeded” present the same number but guide attention differently.

Look for loaded language, vague terms, ambiguous wording, and missing definitions. Ask whether an argument depends on a word changing meaning during the discussion.

A good critical response should also represent opposing views fairly. Before criticizing a position, state it in a form its supporters would recognize. This reduces the risk of creating a straw man.

Reasoning in Mathematics and Science

In mathematics, deductive reasoning is central to proof. In science, reasoning often combines deduction, induction, abduction, measurement, modeling, and uncertainty. A scientific conclusion is strengthened when evidence is reproducible, methods are transparent, and alternative explanations have been tested.

In data interpretation, check axes, units, sample size, and whether a graph shows correlation or causation. A steep-looking line may be caused by a truncated axis. A large percentage increase may describe a small absolute change.

Reasoning in Everyday Decisions

Critical thinking can improve choices without turning every decision into a research project. Match the effort to the importance of the decision.

For a low-stakes choice, a quick comparison may be enough. For a high-stakes decision, gather stronger evidence, compare alternatives, identify risks, and consider what information is still missing.

A useful decision process is:

Define the decision: State the question clearly.
Set criteria: Decide what matters before comparing options.
Gather evidence: Seek information from more than one perspective.
Compare alternatives: Include realistic options, not only extremes.
Rate uncertainty: Identify what you know, what you infer, and what remains unclear.
Review the outcome: After deciding, check what you learned for future decisions.

Respectful Disagreement

Logical reasoning is not the same as “winning.” Productive disagreement aims to understand the issue and improve the quality of conclusions.

Use language that separates people from ideas. You can say, “I do not think that evidence is sufficient because the sample is too small,” rather than insulting the speaker. Ask clarifying questions before assuming what someone means. Admit uncertainty when evidence is limited. If another person provides better reasons, changing your mind is a sign of intellectual responsibility, not weakness.

Interactive Tasks

Quiz: Test Your Knowledge

What is a premise in an argument? (A statement offered as support for a conclusion) (!A statement that must always be false) (!A personal attack on a speaker) (!A question with no possible answer)

When is a deductive argument sound? (When it is valid and all its premises are true) (!When its conclusion is popular) (!When it contains many examples) (!When it uses emotional language)

What does inductive reasoning normally provide? (Probable support for a conclusion) (!Absolute certainty in every case) (!A guarantee without evidence) (!A conclusion unrelated to observations)

Which question best tests confirmation bias? (What evidence would count against my view) (!How can I find only sources that agree with me) (!Why must my first impression be correct) (!How can I ignore alternative explanations)

What is wrong with an ad hominem fallacy? (It attacks the person instead of addressing the argument) (!It uses too much numerical evidence) (!It compares several independent sources) (!It defines important terms clearly)

What is a counterexample used for? (To show that a general claim or reasoning pattern can fail) (!To prove that every possible claim is false) (!To replace all evidence with opinion) (!To make a source more popular)

Why should you check alternative explanations? (Because the same evidence may fit more than one cause) (!Because every explanation is equally good) (!Because causes never matter) (!Because evidence should be ignored)

What does corroboration mean in source evaluation? (Checking whether independent reliable sources support key facts) (!Counting how many times one post was shared) (!Choosing the source with the strongest emotional language) (!Accepting the first result without checking it)

Which statement describes a false dilemma? (It presents only two choices when more options exist) (!It carefully compares several realistic options) (!It supports a claim with multiple relevant sources) (!It distinguishes facts from assumptions)

What is metacognition? (Monitoring and reflecting on your own thinking) (!Memorizing every named cognitive bias) (!Avoiding all disagreement with others) (!Treating confidence as proof)

Memory Game

Premise	A statement offered as support for a conclusion
Validity	A deductive property where true premises cannot lead to a false conclusion
Induction	Reasoning that gives probable rather than guaranteed support
Counterexample	A case that shows a general claim or pattern can fail
Corroboration	Independent support for the same key facts
Metacognition	Reflection on and monitoring of your own thinking

Drag and Drop

Match the correct terms.	Topic
Person attack	Ad hominem
Misrepresented position	Straw man
Only two options	False dilemma
Broad claim from weak sample	Hasty generalization
Popularity treated as proof	Appeal to popularity

Match each reasoning error with the description that best identifies it.

Crossword Puzzle

Premise	What is a supporting statement in an argument called?
Validity	What property does a deductive argument have when true premises cannot lead to a false conclusion?
Induction	What type of reasoning moves from observations toward a probable conclusion?
Fallacy	What is a flaw in reasoning called?
Evidence	What general term means information used to support or test a claim?
Metacognition	What word means thinking about and monitoring your own thinking?

LearningApps

Cloze Text

An argument contains supporting statements called

and a statement they support called the conclusion. A deductive argument is

when true premises cannot lead to a false conclusion. A valid deductive argument with true premises is

. Inductive reasoning provides

rather than guaranteed support. A flaw in reasoning is called a

. Looking for evidence that could challenge your own view helps reduce

. Independent reliable sources can provide

for an important claim. Reflecting on how you reached a judgment is called

.

Open-Ended Tasks

Easy

Claim and reason hunt: Find three claims in a school-safe article or textbook passage. For each claim, identify one stated reason and one question you would ask before accepting it.
Argument sketch: Draw a simple argument map for a decision you make regularly, with one conclusion, two supporting reasons, and one possible objection.
Fallacy poster: Create an image or poster that explains one logical fallacy with an original, school-appropriate example and a corrected version of the reasoning.
Thinking journal: Keep a short one-day record of two moments when you changed your mind, hesitated, or checked evidence, and explain what triggered the change.

Standard

Source comparison: Compare two sources that discuss the same factual topic. Evaluate authorship, evidence, context, purpose, and corroboration, then explain which source is more useful and why.
Reasoning interview: Interview a classmate, teacher, family member, or community member about how they make an important everyday decision. Summarize the criteria, evidence, assumptions, and uncertainty involved.
Mini fact-check: Choose a verifiable claim from a school-safe post or article, trace it to reliable evidence, and produce a short fact-check that distinguishes confirmed facts, uncertainty, and unsupported parts.
Discussion redesign: Record or reconstruct a short disagreement from a fictional or school-safe context, identify weak reasoning or unclear language, and rewrite the exchange as a respectful evidence-based discussion.

Advanced

Argument investigation: Select a debatable school or community issue, collect at least three credible sources with different perspectives, map the strongest arguments on more than one side, and write a justified conclusion.
Bias experiment: Design and carry out a small classroom-safe experiment that tests how framing, anchoring, or order of information may influence choices. Record your method, results, limitations, and ethical safeguards.
Reasoning documentary: Produce a three-to-five-minute video that follows one claim from first impression to evidence check, alternative explanation, counterargument, and revised conclusion. Include a clear source list.
Public reasoning project: Visit a library, museum, council information center, science center, or another relevant public learning place and investigate how evidence is presented to visitors. Create a report evaluating clarity, sourcing, uncertainty, and possible bias.

Learning Assessment

Argument reconstruction assessment: Reconstruct a complex paragraph into premises, assumptions, counterarguments, and conclusion, then explain which step carries the greatest reasoning burden.
Evidence quality assessment: Compare a personal anecdote, a survey summary, a primary document, and an expert review for one claim, then justify how much weight each item deserves and why.
Deduction and induction assessment: Transform one real-world claim into both a deductive argument and an inductive argument, then explain how the standard of evaluation changes between them.
Fallacy repair assessment: Identify a reasoning flaw in a provided argument, explain why the flaw matters, and revise the argument so that the conclusion receives stronger support.
Bias reduction assessment: Given a decision scenario, identify at least two possible cognitive biases and design a checking procedure that could reduce their influence.
Transfer assessment: Apply the same critical-thinking framework to one English language arts text, one scientific claim, and one everyday decision, then compare what counts as strong evidence in each context.

Evidence of Learning

Important evidence of learning includes your ability to identify claims, premises, assumptions, and conclusions; distinguish deductive, inductive, and abductive reasoning; explain validity, soundness, strength, and uncertainty; evaluate the relevance and credibility of evidence; recognize and repair common fallacies; identify possible cognitive biases without using them as personal attacks; compare competing explanations; verify important claims through corroboration; and communicate disagreement fairly.

Strong products may include annotated texts, argument maps, source-evaluation notes, fact-checks, reflective journals, posters, interviews, data displays, experiments, presentations, and videos. Transfer is shown when you can use the same reasoning habits in unfamiliar contexts such as literature, science, mathematics, social studies, digital media, and everyday decisions.