Evaluate Deductive Reasoning and Spot Deductive Fallacies Chapter 8 Evaluate Deductive Reasoning and Spot Deductive Fallacies

Deductive Validity and Language An argument is deductively valid if there is no possibility, real or imaginable: Short of changing the very meanings of the terms and the rules of grammar: That will make the premises all true and the conclusion false © 2013 Pearson Education, Inc. All rights reserved.

Deductive Validity and Language Certain configurations of language form deductively valid argument templates Without violating the meanings of the words/grammatical rules of the language: There is no possible way for the premises all to be true and the conclusion false © 2013 Pearson Education, Inc. All rights reserved.

Deductive Validity and Language Reasoning Deductively about Declarative Statements Denying the Consequent Affirming the Antecedent Disjunctive Syllogism Neither, Unless, and Only © 2013 Pearson Education, Inc. All rights reserved.

Deductive Validity and Language Reasoning Deductively about Classes of Objects Applying a Generalization Applying an Exception The Power of Only One of the most interesting words in the language: © 2013 Pearson Education, Inc. All rights reserved.

Deductive Validity and Language Only has the power to change the meaning of a sentence depending on where it is placed Classes and Objects Reasoning Deductively about Relationships Natural languages are rich with terms that describe relationships © 2013 Pearson Education, Inc. All rights reserved.

Deductive Validity and Language Our understanding of the logical implications of relational terms is part of: Our comprehension of language Transitivity, Reflexivity, and Identity Transitivity Relationship Reflexivity Relationship Identity Relationship © 2013 Pearson Education, Inc. All rights reserved.

Grammatically Equivalent Structures © 2013 Pearson Education, Inc. All rights reserved.

© 2013 Pearson Education, Inc. All rights reserved.

© 2013 Pearson Education, Inc. All rights reserved.

Fallacies Masquerading as Valid Deductive Arguments Just as there are valid argument templates there are fallacious argument templates Precision of thought and expression is the key to avoiding these mistakes in: Our own argument making and also in our evaluation of the arguments offered to us © 2013 Pearson Education, Inc. All rights reserved.

Fallacies Masquerading as Valid Deductive Arguments Fallacies When Reasoning with Declarative Statements Affirming the Consequent Denying the Antecedent The House M.D. Fallacy Fallacies When Reasoning about Classes of Objects © 2013 Pearson Education, Inc. All rights reserved.

Fallacies Masquerading as Valid Deductive Arguments There are logically correct ways of reasoning about classes of objects & their members: There are familiar mistakes we often hear being made False Classification Examples of False Classification seem remarkably abundant © 2013 Pearson Education, Inc. All rights reserved.

Fallacies Masquerading as Valid Deductive Arguments Fallacies of Composition and Division Reasoning about the relationships of parts and wholes can appear to be deductively valid: But fail because the attribute that applies to the parts may not apply to the whole, or vice versa Mistaken Identity © 2013 Pearson Education, Inc. All rights reserved.

Fallacies Masquerading as Valid Deductive Arguments Fallacies that occur when reasoning about relationships like identity, reflexivity, or transitivity: Most often occur when people think they are talking about the same thing, but in fact are not False Reference Create Your Own Deductive Reasoning Examples © 2013 Pearson Education, Inc. All rights reserved.