ABSTRACT
In Chapter 1 we defined and discussed some of the foundational concepts of logic, including the notions of validity and soundness for deductive arguments. An argument form is valid when, if the premises were true, it is impossible for its conclusion to be false. An argument is sound if it is both valid and the premises are true. Validity is a truth-preserving relation. Just as the design of a house can guarantee that a house will withstand violent storms so long as it is constructed of good materials, so a valid form guarantees that its conclusion is true so long as its premises are also true. Validity depends only on the structures of the propositions in an argument. In Chapter 2 we looked at fallacies, common patterns of argument that tend to be psychologically persuasive but which, on analysis, turn out to be unsound.
