# PHIL 210 Study Guide - Quiz Guide: Deductive Reasoning, Modus Ponens

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4 Jun 2020

School

Department

Course

Professor

PHIL 210-Critical Thinking

Book Notes

Chapter 1 The parts of public thinking deductive argument

Study notes 5

➢ Addition

o 1. P

▪ Therefore,

o 2. P or Q.

➢ Ex:

o 1. Foxes are mammals.

▪ Therefore,

o 2. Either foxes are mammals or crows are mammals.

➢ Ex2:

o 1. Foxes are mammals.

▪ Therefore,

o 2. Either foxes are mammals or lizards are mammals

➢ Doesn’t matter is statement adding “or” (Q) is true or false, requires at least one substatement

to be true. If we know that P is true than is garantees that P or Q is true, no matter what Q.

➢ Hypothetical Syllogism

o 1. If P Then Q

o 2. If Q Then R

▪ Therefore,

o 3. If P Then R.

➢ Ex:

o 1. If the dollar is devalued, then export will rise.

o 2. If exports rise, then unemployment will fall.

▪ Therefore,

o 3. If the dollar is devalued, unemployment will fall.

➢ Constructive Dilemma

o 1. P or Q

o 2. If P then R

o 3. If Q then S

▪ Therefore,

o 4. R or S.

➢ Ex:

o 1. Either it will snow tomorrow or there will be a quiz in class.

o 2. If it snows tomorrow, classes will be classed.

o 3. If there’s a quiz in class tomorrow, then ill fail it.

▪ Therefore

o 4. Either class will be cancelled tomorrow or I will fail a quiz tomorrow.

Other Structural Properties of Arguments

Linked arguments