Read
Build the mental model
Move through the guided explanation first so the central distinction and purpose are clear before you evaluate your own work.
Definitions And Concepts
Constructing and Evaluating Definitions
Shows how to build definitions and test them for circularity, scope, obscurity, and usefulness, with a focus on the genus-and-differentia structure and necessary/sufficient conditions.
Read the explanation sections first, then use the activities to test whether you can apply the idea under pressure.
Start Here
What this lesson is helping you do
Shows how to build definitions and test them for circularity, scope, obscurity, and usefulness, with a focus on the genus-and-differentia structure and necessary/sufficient conditions. The practice in this lesson depends on understanding Circularity, Scope, Genus and Differentia, and Necessary and Sufficient Conditions and applying tools such as Fit the Definition to Its Purpose and Avoid Circularity and Obscurity correctly.
How to approach it
Read the explanation sections first, then use the activities to test whether you can apply the idea under pressure.
What the practice is building
You will put the explanation to work through formalization practice, quiz, analysis practice, diagnosis practice, comparison exercise, rapid identification, evaluation practice, and argument building activities, so the goal is not just to recognize the idea but to use it under your own control.
What success should let you do
Construct and revise 4 definitions with explicit checks for type, scope, necessary/sufficient conditions, and circularity.
Reading Path
Move through the lesson in this order
The page is designed to teach before it tests. Use this sequence to keep the reading, examples, and practice in the right relationship.
Study
Watch the move in context
Use the worked examples to see how the reasoning behaves when someone else performs it carefully.
Do
Practice with a standard
Only then move into the activities, using the pause-and-check prompts as a final checkpoint before you submit.
Guided Explanation
Read this before you try the activity
These sections give the learner a usable mental model first, so the practice feels like application rather than guesswork.
Core structure
Genus and differentia
The classical way to build a rigorous definition is the genus-and-differentia structure. You identify a broader class (the genus) that the target belongs to, and then the specific feature (the differentia) that distinguishes it from other members of that class. A square is a rectangle (genus) with four equal sides (differentia). A triangle is a polygon (genus) with exactly three sides (differentia).
The structure is valuable because it makes classification visible. If you cannot think of a natural genus for the term, you probably don't understand its relation to the broader conceptual landscape. If you cannot think of a differentia that actually distinguishes the target, you probably don't understand the term itself well enough to define it.
What to look for
- Identify the broader class the target belongs to.
- Name the feature that distinguishes it from other members of that class.
- Write it as one sentence of the form 'An X is a Y that Z.'
Genus-and-differentia definitions force you to see the concept in its classificatory context.
Analytic core
Necessary and sufficient conditions
A rigorous definition states conditions that are both necessary and sufficient for the term to apply. Necessary means: everything that counts as the thing has this condition. Sufficient means: everything that has this condition counts as the thing. Together, necessary and sufficient conditions pick out exactly the right set.
Most failed definitions fail on one of these two. A too-narrow definition states conditions that are sufficient but not necessary — there are real instances that don't have them. A too-broad definition states conditions that are necessary but not sufficient — some non-instances also have them. Testing your definition against clear cases and borderline cases is how you detect these failures.
What to look for
- Ask whether every instance of the term has the stated condition (necessary).
- Ask whether everything with the stated condition is an instance (sufficient).
- Test against real cases on both sides of the boundary.
A good definition states conditions that are both necessary and jointly sufficient.
Failure patterns
Circularity and obscurity
A definition is circular when the definiens depends on the concept it is supposed to explain. The most obvious form uses the target word itself: 'Justice is the quality of being just.' Subtler forms use near-synonyms: 'A democracy is a democratic political system.' Circular definitions feel informative because they use the same words, but they carry no new information.
A definition is obscure when the definiens is harder to understand than the term being defined. 'A chair is a piece of furniture designed for seated occupancy by a single individual using gravitational stabilization of the lumbar region' is obscure in this sense. A good definition uses simpler, clearer language than the term it defines, not more complex language.
What to look for
- Check that the definiens doesn't use the target term or a near-synonym.
- Check that the definiens is simpler and clearer than the target.
- Read the definition aloud: does it illuminate or just restate?
A good definition explains, simplifies, and clarifies — never restates or obscures.
Practical method
Scope testing with three case types
To test the scope of a definition, run it against three types of cases: clear instances (should be included), clear non-instances (should be excluded), and borderline cases (which reveal the exact shape of the boundary). A definition that handles all three types correctly is well-scoped. One that fails any of them needs revision.
Borderline cases are the most informative. They reveal whether your differentia does real work or just seems to. If your definition of 'sport' classifies chess as a sport but classifies dart-throwing as not-a-sport, you should be able to explain the principled difference — or revise the definition so it handles both consistently.
What to look for
- Test against clear instances (must be included).
- Test against clear non-instances (must be excluded).
- Test against borderline cases (should reveal the boundary).
- Revise if any of the tests fail.
Three case types are enough to expose most scope problems in a candidate definition.
Core Ideas
The main concepts to keep in view
Use these as anchors while you read the example and draft your response. If the concepts blur together, the practice usually blurs too.
Circularity
A defect in which the definiens depends on the very concept it is supposed to explain — directly or through near-synonyms.
Why it matters: Circular definitions fail to illuminate the target concept.
Scope
The range of cases a definition includes or excludes — neither so broad that it admits non-instances, nor so narrow that it excludes real ones.
Why it matters: Definitions should neither include too much nor exclude what properly belongs.
Genus and Differentia
A classical pattern that defines a term by naming a broader class (genus) and the distinguishing feature (differentia) that sets the target apart from other members of that class.
Why it matters: This is a powerful and disciplined structure for many definitions, especially classificatory ones.
Necessary and Sufficient Conditions
A necessary condition is one that must hold for the term to apply; a sufficient condition is one whose holding guarantees the term applies. A good definition typically states conditions that are both.
Why it matters: This pair is the analytic core of rigorous definition construction.
Reference
Open these only when you need the extra structure
How the lesson is meant to unfold
Concept Intro
The core idea is defined and separated from nearby confusions.
Rule Or Standard
This step supports the lesson by moving from explanation toward application.
Worked Example
A complete example demonstrates what correct reasoning looks like in context.
Guided Practice
You apply the idea with scaffolding still visible.
Assessment Advice
Use these prompts to judge whether your reasoning meets the standard.
Mastery Check
The final target tells you what successful understanding should enable you to do.
Reasoning tools and formal patterns
Rules and standards
These are the criteria the unit uses to judge whether your reasoning is actually sound.
Fit the Definition to Its Purpose
A good definition should be judged in light of whether it is lexical, stipulative, precising, theoretical, or persuasive, and whether that type fits the context.
Common failures
- A persuasive definition is used where neutral clarification is needed.
- A lexical definition is demanded where technical precision is required.
Avoid Circularity and Obscurity
A definition should clarify rather than merely repeat or obscure the target concept.
Common failures
- The definition uses the target term or a near-synonym without explanation.
- The wording is more obscure than the term being defined.
Check Scope and Border Cases
A definition should be tested against clear cases, excluded cases, and borderline cases to check for overbreadth and narrowness.
Common failures
- The definition is too broad and includes non-instances.
- The definition is too narrow and leaves out genuine instances.
Aim for Necessary and Sufficient Conditions
A rigorous definition should state conditions that are both necessary (every instance has them) and jointly sufficient (anything having them is an instance).
Common failures
- The definition states only a necessary condition, leaving some cases unclassified.
- The definition states only a sufficient condition, letting other instances slip through.
Patterns
Use these when you need to turn a messy passage into a cleaner logical structure before evaluating it.
Definition Analysis Schema
Input form
proposed_definition
Output form
definition_evaluation
Steps
- Identify the target term (definiendum).
- Identify the kind of definition being used.
- State the intended purpose or context.
- Check for circularity, overbreadth, narrowness, obscurity, and misuse.
- Test the definition against clear cases, excluded cases, and border cases.
- Revise the definition if needed.
Watch for
- Evaluating all definitions as if they had the same purpose.
- Ignoring whether the definition fits the intended scope.
Genus-and-Differentia Builder
Input form
target_concept
Output form
structured_definition
Steps
- Identify the broader class to which the thing belongs.
- Identify the distinguishing feature that sets it apart from other members of that class.
- Draft the definition in one sentence of the form 'An X is a Y that Z.'
- Test the definition against clear cases and borderline cases.
- Revise for scope and clarity.
Watch for
- Naming a differentia that is too broad to distinguish the target.
- Choosing a genus that is too remote or too narrow.
Worked Through
Examples that model the standard before you try it
Do not skim these. A worked example earns its place when you can point to the exact move it is modeling and the mistake it is trying to prevent.
Worked Example
A Circular Definition and Its Repair
A definition should explain, not merely restate. Testing with case types exposes where the definition still needs work.
Problem
The definiens repeats the target concept without clarifying it. 'Just' is a direct cognate of 'justice,' so the definition is perfectly circular — it carries no information.
Test Cases
Borderline
An employer paying two employees differently because one negotiated harder — reveals that the definition needs more work on what 'relevant standards' means.
Clear Case
A judge applying the same penalty to two people who committed the same offense — fits.
Clear Non Case
A judge applying a harsher penalty to one person because of her race — correctly excluded as unjust.
Better Start
Justice is the fair and principled treatment of persons under relevant standards, especially when applying rewards, penalties, and rights.
Bad Definition
Justice is the quality of being just.
Worked Example
Genus-and-differentia in action
The genus-and-differentia structure produces a clean, testable definition in one sentence.
Term
Square
Genus
rectangle
Definition
A square is a rectangle with four equal sides.
Test Cases
Borderline
A rhombus with all angles slightly off 90° — excluded because it's not a rectangle.
Clear Case
A 5 cm × 5 cm rectangle — fits.
Clear Non Case
A 5 cm × 3 cm rectangle — correctly excluded.
Differentia
with four equal sides
Pause and Check
Questions to use before you move into practice
Self-check questions
- Does the definition include only the right cases?
- Does it exclude clear non-cases?
- Does it explain the term without circularity?
- Is the definiens simpler than the definiendum?
Practice
Now apply the idea yourself
Move into practice only after you can name the standard you are using and the structure you are trying to preserve or evaluate.
Formalization Practice
FoundationsBuild and Evaluate a Definition
For each term, draft a definition using genus and differentia, identify the type and purpose, and evaluate it for scope, circularity, obscurity, and practical fit. Revise it if needed.
Three terms to define and test
For each case, your draft should use genus-and-differentia structure when appropriate. Test the draft against clear cases and borderline cases before revising.
Case A — Excused absence (student handbook)
A student handbook needs a working definition of 'excused absence' for attendance appeals. The stakes are modest but real — this definition decides whether students can make up work.
This calls for a precising definition with clear boundaries. What counts as an excused absence, and what doesn't?
Case B — Friendship (philosophy club)
A philosophy club is discussing what should count as 'friendship' in a serious conversation about loyalty and trust. This is conceptual analysis, not policy.
Try a genus-and-differentia structure. What's the broader category, and what distinguishes friendship from acquaintanceship or alliance?
Case C — Plagiarism (integrity policy)
A classroom integrity policy needs a definition of 'plagiarism' that is clear enough to guide real student decisions. Students need to know what they can and can't do.
Look for scope problems: the definition must include genuine cases of plagiarism without sweeping in legitimate citation, paraphrase, or collaboration.
Use one of the items above. State the target term, draft the definition you want to test, and explain whether it is too broad, too narrow, circular, or on target.
Quiz
FoundationsScenario Check: Constructing and Evaluating Definitions
Each question presents a scenario or challenge. Answer in two to four sentences. Focus on showing that you can use what you learned, not just recall it.
Scenario questions
Work through each scenario. Precise, specific answers are better than long vague ones.
Question 1 — Diagnose
A student makes the following mistake: "Using the target word or a near-synonym in the definiens." Explain specifically what is wrong with this reasoning and what the student should have done instead.
Can the student identify the flaw and articulate the correction?
Question 2 — Apply
You encounter a new argument that you have never seen before. Walk through exactly how you would build genus differentia definition, starting from scratch. Be specific about each step and explain why the order matters.
Can the student transfer the skill of build genus differentia definition to a genuinely new case?
Question 3 — Distinguish
Someone confuses circularity with scope of definition. Write a short explanation that would help them see the difference, and give one example where getting them confused leads to a concrete mistake.
Does the student understand the boundary between the two concepts?
Question 4 — Transfer
The worked example "A Circular Definition and Its Repair" showed one way to handle a specific case. Describe a situation where the same method would need to be adjusted, and explain what you would change and why.
Can the student adapt the demonstrated method to a variation?
Use one of the items above. State the target term, draft the definition you want to test, and explain whether it is too broad, too narrow, circular, or on target.
Analysis Practice
FoundationsApply the Concepts: Constructing and Evaluating Definitions
Analyze each passage below using the concepts from this lesson. Identify key logical features and explain your reasoning.
Practice scenarios
Work through each scenario carefully. Apply the concepts from this lesson.
Scenario 1
A local council argues: every park that has been surveyed shows declining bird populations. The marsh reserve has not been surveyed. Therefore, we cannot conclude anything about its bird population.
Scenario 2
The professor told the class: 'Either your hypothesis is testable, or it does not belong in a scientific paper.' Maria's hypothesis predicts no observable outcomes.
Scenario 3
A fitness study concludes that runners who stretch before exercise report fewer injuries. However, runners who stretch may also be more cautious in other ways.
Pick one of the passages above and map how the reasons are supposed to support the conclusion.
Diagnosis Practice
FoundationsSpot the Error: Constructing and Evaluating Definitions
Each passage contains a logical mistake. Identify the error, name it if possible, and explain why the reasoning fails.
Practice scenarios
Work through each scenario carefully. Apply the concepts from this lesson.
Case A
Everyone at the meeting agreed the policy is fair. Since the meeting was open to the public, we can say the public agrees the policy is fair.
Case B
No reptile is a mammal. No mammal is an insect. Therefore, no reptile is an insect.
Case C
The forecast said 70% chance of rain. It did not rain. Therefore, the forecast was wrong.
Use one of the passages above. Name the weakness, explain the violated standard, and show how the reasoning should be repaired.
Comparison Exercise
FoundationsCompare and Connect: Constructing and Evaluating Definitions
Compare the reasoning in the passages below. Identify similarities, differences, and which argument is stronger, explaining your criteria.
Practice scenarios
Work through each scenario carefully. Apply the concepts from this lesson.
Argument X
Since all observed swans in Europe were white, all swans are white.
Argument Y
Since the chemical formula for water is H2O in every sample we have tested, water is H2O.
Argument Z
Since every student I asked preferred online classes, all students prefer online classes.
Use one of the items above. State the target term, draft the definition you want to test, and explain whether it is too broad, too narrow, circular, or on target.
Analysis Practice
FoundationsDeep Practice: Constructing and Evaluating Definitions
Apply the concepts from this lesson to more complex scenarios. Work through each carefully and explain your reasoning in full.
Advanced practice scenarios
Each scenario tests your ability to apply foundational logic concepts in realistic contexts.
Case 1
An editorial argues: 'Standardized testing must be eliminated because it causes student anxiety. And since anything that causes anxiety is harmful, standardized testing is harmful.' Analyze the argument's structure, identify any hidden premises, and evaluate its strength.
Case 2
A scientist writes: 'We observed that 90% of treated mice recovered, while only 30% of untreated mice recovered. The treatment appears effective. However, the treated group was also younger on average.' Identify the argument, the potential confounder, and what additional information would strengthen or weaken the conclusion.
Case 3
A philosopher claims: 'Either free will is an illusion, or moral responsibility is justified. Neuroscience has shown that brain activity precedes conscious decisions. Therefore, free will is probably an illusion, and moral responsibility may not be justified.' Map the logical structure and evaluate whether the conclusion follows.
Pick one of the passages above and map how the reasons are supposed to support the conclusion.
Analysis Practice
FoundationsReal-World Transfer: Constructing and Evaluating Definitions
Apply what you have learned to these real-world contexts. Analyze each scenario using the tools and concepts from this lesson.
Transfer practice
Connect the concepts from this lesson to contexts outside the classroom.
Media literacy
A social media post claims: 'A new study proves that video games improve intelligence.' The post links to a study of 40 college students who played puzzle games for 2 weeks and showed improved scores on one type of spatial reasoning test. Evaluate this claim using what you know about arguments, evidence, and reasoning.
Everyday reasoning
A friend argues: 'I should not get vaccinated because my cousin got vaccinated and still got sick. Also, I read an article that said natural immunity is better.' Identify the types of reasoning, assess their strength, and explain what additional evidence would be relevant.
Professional context
A manager says: 'Our last three hires from University X performed well, so we should recruit exclusively from University X.' Analyze the reasoning type, identify potential problems, and suggest a better approach.
Pick one of the passages above and map how the reasons are supposed to support the conclusion.
Rapid Identification
FoundationsTimed Drill: Constructing and Evaluating Definitions
Work through these quickly. For each passage, identify whether it contains an argument, name its type if so, and point to the conclusion. Aim for speed and accuracy.
Quick-fire argument identification
For each item, decide: argument or not? If yes, what type and what is the conclusion? Under 45 seconds per item.
Item 1
The bridge was built in 1962. It was designed by a local engineering firm and cost $2.3 million.
Item 2
Because the experiment was not replicated, the results should be treated with caution.
Item 3
Sharks have survived five mass extinction events, so they are remarkably resilient species.
Item 4
If the evidence was obtained illegally, the court must exclude it. The evidence was obtained without a warrant. Warrantless searches are illegal. Therefore, the court must exclude the evidence.
Item 5
The town council meets every second Tuesday. This week is the second Tuesday. The library will be used for the meeting.
Item 6
The most likely reason the power went out is the thunderstorm, since the outage started exactly when lightning struck the transformer.
Use one of the items above. State the target term, draft the definition you want to test, and explain whether it is too broad, too narrow, circular, or on target.
Evaluation Practice
FoundationsPeer Review: Constructing and Evaluating Definitions
Below are sample student attempts to identify and analyze arguments. Evaluate each response: Is the identification correct? Is the analysis accurate? What feedback would you give?
Evaluate student argument analyses
Each student tried to break down an argument into premises and conclusion. Assess their work.
Student A's work
Passage: 'Since exercise reduces stress and stress causes health problems, exercise prevents health problems.' Student A wrote: 'Premise 1: Exercise reduces stress. Premise 2: Stress causes health problems. Conclusion: Exercise prevents health problems. This is a valid deductive argument.'
Student B's work
Passage: 'The committee should approve the budget because it was prepared by experts.' Student B wrote: 'This is not an argument. It is just a recommendation.'
Student C's work
Passage: 'Most doctors recommend regular check-ups. Regular check-ups catch diseases early. Early detection saves lives. Therefore, you should get regular check-ups.' Student C wrote: 'Premise 1: Most doctors recommend check-ups. Conclusion: You should get check-ups. This is an inductive argument from authority.'
Student D's work
Passage: 'It will probably rain tomorrow because the barometric pressure is dropping and clouds are moving in from the west.' Student D wrote: 'Premise 1: Barometric pressure is dropping. Premise 2: Clouds are moving in. Conclusion: It will probably rain. This is an inductive argument based on observed indicators. Strength: moderate, since weather patterns are not perfectly predictable.'
Choose one of the passages above and evaluate it using the right standard for its reasoning mode.
Argument Building
FoundationsConstruction Challenge: Constructing and Evaluating Definitions
Build arguments from scratch. For each task, construct a well-structured argument with clear premises and a conclusion. Identify the reasoning type you are using.
Construct original arguments
For each prompt, build a complete argument from scratch. Clearly state premises, conclusion, and reasoning type.
Task 1
Construct a deductive argument with two premises that concludes: 'This substance is not an acid.' Make sure the argument is valid.
Task 2
Build an inductive argument with at least three pieces of evidence supporting the conclusion: 'Regular reading improves vocabulary.' Make it as strong as you can.
Task 3
Construct an argument that uses an indicator word for the conclusion and a different indicator word for at least one premise. The topic should be about environmental policy.
Task 4
Build two different arguments for the same conclusion: 'Public libraries should remain publicly funded.' One argument should be deductive, the other inductive. Explain why one might be more persuasive than the other.
Use one of the items above. State the target term, draft the definition you want to test, and explain whether it is too broad, too narrow, circular, or on target.
Diagnosis Practice
FoundationsCounterexample Challenge: Constructing and Evaluating Definitions
For each argument, construct a counterexample or identify a scenario that shows the reasoning is flawed. Explain what the counterexample reveals about the argument's weakness.
Counterexamples and edge cases
Each argument has a flaw. Expose it with a specific counterexample.
Argument 1
Every time I have washed my car, it rained the next day. Therefore, washing my car causes rain.
Argument 2
No one at the party complained about the food. Therefore, everyone enjoyed the food.
Argument 3
This policy worked well in Sweden. Therefore, it will work well in Brazil.
Argument 4
The candidate won 60% of the vote in the primary. Therefore, they will win the general election.
Argument 5
All the reviews on the website are positive. Therefore, the product is excellent.
Use one of the passages above. Name the weakness, explain the violated standard, and show how the reasoning should be repaired.
Analysis Practice
FoundationsIntegration Exercise: Constructing and Evaluating Definitions
These exercises connect the concepts from this lesson to ideas across different reasoning domains. Apply foundational concepts to scenarios that require multiple analytical tools.
Cross-cutting foundational exercises
Each scenario tests your ability to apply foundational logic concepts alongside other analytical skills.
Scenario 1
A news article reports: 'Scientists have proven that coffee is good for you, according to a new study of 500 adults who drink coffee daily.' Identify all arguments in this claim, classify the reasoning type(s), evaluate the evidence quality, and explain what additional information would be needed.
Scenario 2
A school board argues: 'Since standardized test scores are the best measure of student learning, and our test scores have risen 10% this year, our educational quality has improved.' Identify the premises and conclusion, classify the reasoning, spot any hidden assumptions, and construct an alternative explanation for the score increase.
Scenario 3
A city planner argues: 'If we build more bike lanes, more people will bike. More biking reduces car traffic. Less car traffic means less pollution. Therefore, building bike lanes will reduce pollution.' Map the argument structure, evaluate each inferential step separately (some may be deductive, others inductive), and identify the weakest link.
Scenario 4
An investor reasons: 'This company's stock has risen every year for the past eight years. The CEO is talented and the industry is growing. I should invest heavily.' Identify all reasoning types present, evaluate each one, and explain how the different types of reasoning interact in this argument.
Pick one of the passages above and map how the reasons are supposed to support the conclusion.
Diagnosis Practice
FoundationsMisconception Clinic: Constructing and Evaluating Definitions
Each item presents a common misconception about arguments, reasoning, or logic. Identify the misconception, explain why it is wrong, and state the correct principle.
Common logic misconceptions
Diagnose and correct each misconception about basic logic and arguments.
Misconception 1
A student says: 'An argument with true premises must have a true conclusion.'
Misconception 2
A student claims: 'If two people disagree, at least one of them must be using bad logic.'
Misconception 3
A student writes: 'Opinions cannot be arguments because arguments require facts, not opinions.'
Misconception 4
A student argues: 'A strong argument is one that is persuasive. If people are convinced by it, it must be a good argument.'
Misconception 5
A student says: 'An explanation and an argument are the same thing -- both provide reasons for something.'
Use one of the passages above. Name the weakness, explain the violated standard, and show how the reasoning should be repaired.
Analysis Practice
FoundationsScaffolded Analysis: Constructing and Evaluating Definitions
Build an argument analysis in stages. Each task provides a passage and walks you through the analysis process step by step. Complete each stage before moving on.
Step-by-step argument analysis
Analyze each argument progressively, one skill at a time.
Scaffold 1
Passage: 'Because violent crime has increased 15% this year and the police budget was cut 10% last year, the budget cuts are responsible for the crime increase. Therefore, the city council should restore police funding.' Stage 1: Identify all premises and the conclusion. Stage 2: Classify the reasoning type. Stage 3: Identify any hidden premises or assumptions. Stage 4: Evaluate the strength of the inference. Stage 5: Suggest what additional evidence would strengthen or weaken this argument.
Scaffold 2
Passage: 'Three out of four dentists recommend this toothpaste. Since expert opinion is reliable, you should use this toothpaste. After all, if experts recommend something, it must be good.' Stage 1: Put the argument in standard form. Stage 2: Identify the reasoning type for each inferential step. Stage 3: Spot any logical errors or questionable assumptions. Stage 4: Rewrite the argument to make it stronger.
Scaffold 3
Passage: 'Countries that invest in education have stronger economies. Our country should invest more in education to strengthen the economy. This is proven by the examples of South Korea, Finland, and Singapore.' Stage 1: Map the argument structure. Stage 2: Identify whether this is primarily deductive, inductive, or abductive. Stage 3: Evaluate the evidence. Stage 4: Identify the strongest objection to this argument. Stage 5: Revise the argument to address that objection.
Pick one of the passages above and map how the reasons are supposed to support the conclusion.
Analysis Practice
FoundationsSynthesis Review: Constructing and Evaluating Definitions
These exercises combine everything you have learned about arguments, reasoning types, and evaluation. Each scenario requires you to identify, classify, analyze, evaluate, and improve an argument.
Comprehensive foundations review
Apply all foundational logic skills together.
Comprehensive 1
A school district superintendent argues: 'Our district should adopt year-round schooling. Studies show students in year-round schools retain 10% more knowledge. Teachers in year-round districts report higher job satisfaction. The only objection is tradition, but tradition is not a good reason to hold back progress. Other districts that switched have seen rising test scores within two years.' Perform a complete analysis: identify all premises and the conclusion, classify each reasoning step, find any hidden assumptions, spot any logical errors, evaluate the overall strength, and rewrite the argument to make it stronger.
Comprehensive 2
A debate transcript: Speaker A says 'Social media causes depression -- the data is clear.' Speaker B responds 'That is correlation, not causation. Besides, my teenagers use social media constantly and they are perfectly happy.' Speaker A replies 'Your children are exceptions. The overall trend is undeniable.' Analyze each speaker's reasoning: identify argument types, evaluate their strength, identify logical errors, find hidden assumptions, and draft what a well-reasoned third speaker should say.
Pick one of the passages above and map how the reasons are supposed to support the conclusion.
Animated Explainers
Step-by-step visual walkthroughs of key concepts. Click to start.
Read the explanation carefully before jumping to activities!
Further Support
Open these only if you need extra help or context
Mistakes to avoid before submitting
- Confusing rhetorical force with conceptual precision.
- Testing only with easy clear cases and skipping borderline cases.
Where students usually go wrong
Using the target word or a near-synonym in the definiens.
Drafting a definition so broad that obvious non-instances are included.
Making the definition so narrow that central cases are excluded.
Making the definiens more obscure than the term being defined.
Historical context for this way of reasoning
Aristotle
Aristotle's emphasis on genus and differentia still matters because it encourages definitions that classify and distinguish with discipline. His method remains the backbone of modern dictionary definitions and scientific nomenclature.