Universal affirmative: Difference between revisions
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[[Universal affirmative]]s can only be partially converted. “All of Alma Cogan is dead, but only some of the class of dead people are Alma Cogan.” | [[Universal affirmative]]s can only be partially converted. “All of Alma Cogan is dead, but only some of the class of dead people are Alma Cogan.” | ||
As Monty Python had it, given the premise, "all fish live underwater" and "all mackerel are fish", one cannot conclude | As Monty Python had it, given the premise, "all fish live underwater" and "all mackerel are fish", one cannot conclude that "if you buy kippers it will not rain", or that "trout live in trees", much less that "I do not love you any more." | ||
{{sa}} | {{sa}} | ||
*[[Correlation]] and [[causation]] | *[[Correlation]] and [[causation]] | ||
Revision as of 19:50, 20 October 2019
A universal affirmative is a categorical statement taking the form: “Every A is B.” where A and B are predicates. In the language of predicate logic, this can be expressed as: ∀x:A(x)⟹B(x).
Universal affirmatives can only be partially converted. “All of Alma Cogan is dead, but only some of the class of dead people are Alma Cogan.”
As Monty Python had it, given the premise, "all fish live underwater" and "all mackerel are fish", one cannot conclude that "if you buy kippers it will not rain", or that "trout live in trees", much less that "I do not love you any more."
See also
- Correlation and causation