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

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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
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