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

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4 Jun 2020

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PHIL 210-Critical Thinking

Book Notes

Chapter 1 The parts of public thinking deductive argument

Study notes 4

➢ Arguments that is Invalid and Not Sound

o 1. 42 is number.

o 2. Continents Drift.

o 3. Pigs grunt.

▪ Therefore,

o 4. Socrates is Greek

➢ . P1, P2, and P3 are all true, the conclusion is true as well. But the premises do not relate

to nor do they support the conclusion, therefore it is not valid, therefore not sound.

➢ Argument that is Sound

o 1. Vixens are foxes.

o 2. All foxes are mammals.

▪ Therefore

o 3. Vixens are mammals.

➢ The premises relate to and supports the conclusion in a way that is premises are true

conclusion is true, therefore is it Valid, All the premises are true.

o This argument is sound. This is also an example of an argument framed in

categorical terms: manner of how the categories vixen, fox, and mammal are

related.

➢ Conditional Reasoning: ( If P then Q )

➢ Quantifier Expression: ( like “some” and “every”) – the previous example

➢ Variable: ( like x or y – kind of place holder for objects that could be plugged into the

statement)

o Ex:

▪ 1. For every object x, if x is a vixen then x is a fox.

▪ 2. For every object x, if x is a fox then x is a mammal.

• Therefore

▪ 3. For every object x, if x is a vixen then x is a mammal

➢ Hypothetical Syllogism

o 1. If P, then Q.

o 2. If Q, then Z.

▪ Therefore,

o 3. If P then Z.

➢ Disjunctive Syllogism

o 1. P or Q.

o 2. Not Q.

▪ Therefore,