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Categorical Logic. A useful type of “real world” logic commonly used for characterizing relationships Applications in law, business contracts, natural and social sciences. Categorical Claims. A: All X are Y All means “Every single one, no exceptions.” “And there is at least one.”.
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Categorical Logic • A useful type of “real world” logic commonly used for characterizing relationships • Applications in law, business contracts, natural and social sciences
Categorical Claims • A: All X are Y All means “Every single one, no exceptions.” “And there is at least one.”
Categorical Claims • A: All X are Y In natural language: Every X is a Y. Each X is a Y. If it is an X, then it is a Y. All Xs are Ys. Any X is a Y. All non-Ys are non-Xs. Only Ys are Xs The only Xs are Ys
Categorical Claims • A: All X are Y In natural language: Every X is a Y. Each X is a Y. If it is an X, then it is a Y. All Xs are Ys. Any X is a Y. All non-Ys are non-Xs. Only Ys are Xs The only Xs are Ys Note: X and Y must be nouns or noun phrases.
Categorical Claims • A: All X are Y • E: No X are Y
Categorical Claims • A: All X are Y • E: No X are Y • I: Some X are Y
Categorical Claims • A: All X are Y • E: No X are Y • I: Some X are Y Note: The range of “some” in categorical logic is from as few as one to as many as all of the things in the category.
Categorical Claims • A: All X are Y • E: No X are Y • I: Some X are Y • O: Some X are not Y
Categorical Claims The direct way of reasoning with ALL All S are P A is s VALID Therefore, a is P
Categorical Claims Reasoning in a chain with All All S are P All P are Q VALID Therefore, all S are Q (This works with All not Some)
Categorical Claims Direct way of reasoning with NO All S are P No Q is a P VALID Therefore, no Q is a S