 ARGUMENTS  LANGUAGE  FALLACIES
 CATEGORICAL PROPOSITIONS  

LOGIC HOME QUIZZES 
Appendix A: Notes on Truth, Validity, and Soundness I. Definitions and Rules. A. Definitions. 1. Argument: any group of propositions of which one is claimed to follow
logically from the others. B. Rules. 1. A deductive argument is valid only if its conclusion follows necessarily from its
premisses. II. Problems and Examples A. The following examples serve to show the possible combinations of truth values in valid categorical syllogisms.
Examples: Case 1: Case 2: Case 3: Case 4: B. The following examples serve to show the possible combinations of truth values in invalid categorical syllogisms. Note that every combination of truth values is possible in invalid arguments.
Examples: Case 1: Case 2: Case 3: Case 4: C. All of the following statements are true. Study each carefully. Refer to the above outline to see how each statement is true. 1. A sound deductive argument is a deductive argument which is valid and whose premiss(es) are true. (Cf., A: 1 above.) 2. It is possible for a deductive argument to be both valid and unsound. (Cf., A: 2, 4 above.) 3. If a deductive argument is sound, it cannot be invalid. (Cf., A: 1, 3 above). 4. If the premisses of a deductive argument are true, then the argument can be valid or invalid. (Cf., A: 1; B: 1, 3 above.) 5. If the conclusion of a deductive argument is true, then the premisses can be true or false. (Cf., A: 1, 2; B: 1, 2 above.) 6. If a deductive argument is sound, then its conclusion must be true. (Cf., A: 1, 3 above.) 7. If the premisses of a deductive argument are true, then the conclusion can be true or false. (Cf., A: 2, 4; B: 2, 4 above.) 8. If a deductive argument has a false premiss, then it must be unsound. (Cf., A: 2, 4; B: 2, 4 above.) 9. If a deductive argument is valid, then its conclusion can be true or false. (Cf., A: 1, 2, 4 above.) 10. If every proposition in a deductive argument is true, then the argument can be sound or unsound. (Cf., A: 1; B: 1 above.)
