Stage Six- Introduction to Deduction

Logical Form - sentences

  • The logical form of a sentence is its structure, without reference to its content (what it is about).

  • Logical structure is composed of two parts - variables for sentences (p, q, r), and logical connectives (not, and, or, if-then).

  • Start by identifying all logical connectives in a sentence. The parts that are left are assigned variables.

Logical form - arguments

  • Modus Ponens: If P, then Q. P, therefore Q.

  • Modus Tollens: If P, then Q. Not Q, therefore not P.

  • Disjunctive Syllogism: P or Q. Not P, therefore, Q.

  • Hypothetical Syllogism: If P, then Q. If Q, then R. Therefore, if P, then R.

  • Dilemma: P or Q. If P, then R. If Q, then R. Therefore, R.

examples

  • Example #1 (0:00) - sentence translation (easy)

  • Example #2 (2:07) - sentence translation (medium)

  • Example #3 (3:25) - sentence translation (hard)

  • Example #4 (5:27) - argument translation