MODR 1760 Lecture Notes - Lecture 6: Obversion, Contraposition, Middle Term
30 Oct 2018
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Immediate inferences: valid or equivalent sentences (equivalent operations, 3 kinds: conversion, obversion, contraposition. Conversion: switch the position of subject with predicate, given all s are p- the converse will be- all p are s. The converse is not equivalent to the original sentences. In an a-type sentence, the converse in not equivalent it"s invalid inference. Exp: all flowers are plants. (all s are p. ) All plants are flowers. (all p are s. : given no s are p- the converse no p are s. In an e-type sentence, the converse is equivalent its valid inference. Exp: no snakes are humans. (no s are p. ) No humans are snakes. (no p are s. ) 1: given some s are p- the converse- some p are s. In an i-type sentence, the converse is equivalent its valid inference. Some p are s: given some s are not p- the converse- some p are not s.
