Fallacies And Errors·Rigorous·5 lessons·~340 min

Fallacies and Reasoning Errors

From fundamental inferential failures to specific species across modes of reasoning

Start the first lesson Back to curriculum

What you'll learn

By the end of this unit, you can…

Classify fallacy families.
Identify species by reasoning mode.
Repair fallacious reasoning.
Apply charitable reading before diagnosis.

Lessons

Lesson sequence

1
Fundamental Fallacy Families
Introduces a structural taxonomy of fallacies by fundamental inferential defect rather than by disconnected labels, and establishes the diagnosis-and-repair routine used throughout the unit.
15 activities5 worked examples
Open →
2
Deductive and Formal Fallacies
Examines fallacies driven by formal structure, quantifier scope, class reasoning, and invalid deductive patterns, and shows why these errors demand structural rather than evidential repair.
18 activities5 worked examples
Student Pro
3
Inductive, Abductive, and Best-Explanation Fallacies
Shows how support miscalibration and option-space failure produce different species across evidence-based reasoning, and why good diagnosis has to track the mode of inference.
15 activities5 worked examples
Student Pro
4
Bayesian and Problem-Solving Fallacies
Extends the taxonomy to probabilistic updating and practical strategy selection, showing how base-rate neglect and option-space failure behave across both domains.
15 activities5 worked examples
Student Pro
5
Capstone: Diagnosing, Repairing, and Communicating Fallacies
An integrative lesson that asks students to run the full diagnostic cycle on arguments drawn from the wild: name the fallacy, explain the mechanism of failure, and propose a repair or a steelman when one is available.
2 activities1 worked example
Student Pro

How to study

Three moves that work for this unit

Read the explanation

Each lesson opens with a guided walkthrough — read it before the activity.

Study the worked example

Look at why each step follows, not just what the answer is.

Practice with the target in mind

Know which rule applies and what would make the response weak before you start.

Reference materials

Optional context for the unit. Each lesson surfaces the concepts and rules it uses — these are here when you want the bigger picture.

Concept map (7 terms)

Fundamental Fallacy

A broad family of inferential failure that can generate several more specific named fallacies.

Species of a Fallacy

A more specific recurring error pattern that instantiates a broader fundamental inferential defect.

Relevance Failure

A family of errors in which the offered consideration does not bear on the conclusion in the required way.

Support Miscalibration

A family of errors in which the degree or type of support claimed is stronger, weaker, or otherwise different from what the evidence actually warrants.

Scope or Structure Failure

A family of errors caused by misreading logical form, quantifier scope, class structure, or formal relation.

Option-Space Failure

A family of errors in which relevant alternatives, constraints, or strategy revisions are ignored.

Diagnosis and Repair

The practice of pairing any fallacy identification with a description of what change would make the reasoning acceptable.

Rules and standards (4)

Trace the Species Back to the Family. A correct fallacy diagnosis should identify both the specific named error and the broader inferential defect it exemplifies. Common failures: The learner memorizes labels without understanding the violated standard.; Two fallacies are treated as unrelated even though they share the same deeper defect..
Diagnose by the Mode of Reasoning. The same surface error term may need different analysis depending on whether the reasoning is deductive, inductive, abductive, Bayesian, or practical. Common failures: A probabilistic error is judged as though it were purely deductive.; A problem-solving failure is mislabeled with a rhetorical fallacy name while ignoring strategic structure..
Repair Rather Than Merely Label. A strong fallacy analysis should explain what inferential repair would be required for the argument to meet the relevant standard.

Fallacies and Reasoning Errors

By the end of this unit, you can…

Lesson sequence

Fundamental Fallacy Families

Deductive and Formal Fallacies

Inductive, Abductive, and Best-Explanation Fallacies

Bayesian and Problem-Solving Fallacies

Capstone: Diagnosing, Repairing, and Communicating Fallacies