Deductive ReasoningDeductive Reasoning

Chapter 2Chapter 2

Lesson 4Lesson 4

Deductive ReasoningDeductive Reasoning

The process of reasoning logically The process of reasoning logically from given statements or facts to a from given statements or facts to a conclusion.conclusion.

It is also called logical reasoningIt is also called logical reasoning

Law of DetachmentLaw of Detachment

If the hypothesis of a true conditional If the hypothesis of a true conditional is true, then the conclusion is true.is true, then the conclusion is true.

If the conditional is true and P is true If the conditional is true and P is true then Q must be true.then Q must be true.

Law of SyllogismLaw of Syllogism

Allows you to state a conclusion from Allows you to state a conclusion from two true conditional statements two true conditional statements when the conclusion of one when the conclusion of one statement is the hypothesis of the statement is the hypothesis of the other statement.other statement.

Meaning if P then Q is true, and if Q Meaning if P then Q is true, and if Q then R is true, then if P then R must then R is true, then if P then R must be true.be true.

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Look at Problem 2 for an example of Look at Problem 2 for an example of use of the law of Syllogismuse of the law of Syllogism