Deductive reasoning
Deduction is the part of reasoning where conclusions are forced rather than suggested. Knowing which moves are guaranteed, and which only feel guaranteed, is the whole subject.
What you'll learn
10 chapters, then the quiz
- 01What an argument isPremises, conclusion, structure.
- 02Validity and soundnessTwo different questions.
- 03If, thenThe two valid moves and two invalid ones.
- 04All, some, noneCategorical reasoning.
- 05Necessary and sufficientThe distinction that clarifies arguments.
- 06Deduction against inductionGuaranteed against likely.
- 07Formal fallaciesInvalid shapes that feel valid.
- 08Informal fallaciesWrong for reasons other than structure.
- 09Logic puzzlesDeduction under constraints.
- 10Using it in real argumentsWhere the disagreement actually is.
More math & logic tests
See all →- Easy
Mental math sprint
Arithmetic you should be able to do without reaching for a calculator.
8 questions5 min - Hard
Logic puzzles
Short problems where the obvious answer is usually the wrong one.
7 questions9 min - Medium
Probability basics
Coins, dice and cards, plus the traps that come with them.
7 questions7 min