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Week 5 · Module overview

Week 5 — Categorical Reasoning

Critical Thinking Free sample edition

Welcome to your Week 5 Start Here page.

Why this matters

A nursing student checking which patients a safety rule covers and a business major reading a store's return policy both need to know exactly what "all", "no", and "some" claim about a group.

In plain language

This week is about claims that sort things into groups, such as "all members may vote" or "some desserts contain nuts." You will learn four sentence patterns for these claims, the categorical forms (the four ways of saying that a group is inside, outside, or partly inside another group). You will put two such claims together to reach a third, in an argument called a categorical syllogism (a three-line argument about three groups). Then you will test that argument with a Venn diagram (a drawing of overlapping circles, one for each group). Reading "all" and "some" carefully keeps you from flipping a rule around and drawing a conclusion it never gave you.

  • Already covered: Week 4 taught you the valid "if" forms and the two formal fallacies.
  • This week: the four categorical forms, syllogisms, and the Venn test.
  • How they connect: an open region in a diagram is room for a counterexample.
  • Where we're going next: Week 6, Language and Meaning.

Focus

What do "all", "no", and "some" really claim, and which arguments built on them hold?

By the end of this module, you should be able to:

  • [ ] write a claim in each of the four categorical forms
  • [ ] rewrite an "only" claim with the right group as predicate
  • [ ] name the minor, major, and middle terms of a syllogism
  • [ ] test a syllogism with a Venn diagram described in words

To-do

Plan your week

  1. Read Chapter 5 (about 40 minutes), then the lecture and slides.
  2. Work the lecture tutorial (60–90 minutes) and the practice set (about 20 minutes).
  3. Do the Argument Workshop (about 90 minutes), the discussion, and the assignment.
  4. Take the quiz.

This week's checkpoint: explain why the poodle syllogism is invalid by naming the region it leaves open.

You've got this

Take it in order, and ask your instructor if a step snags.

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