Other immediate inferences — material obversion, Inference by Added Determinants, Inference by Complex Conception & Inference by Converse Relation

“A mouse is an animal, therefore a big mouse is a big animal.” That sounds exactly like the pattern you just learned in eduction — add the same word to both sides — yet it is false: a big mouse is nowhere near a big animal. This last group of immediate inferences is where logic teaches you the traps hiding inside patterns that otherwise look perfectly safe.

In two minutes

Beyond opposition and formal eduction, this syllabus recognises four further one-premise inferences: material obversion (using a real, specific contrary instead of a bare logical negative), inference by added determinants (attaching an identical qualifier to both subject and predicate), inference by complex conception (attaching an identical complex idea to both terms), and inference by converse relation (restating a relational proposition from its reverse side).

The rest of this chapter

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