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Single Idea 18831

[from 'The Boundary Stones of Thought' by Ian Rumfitt, in 11. Knowledge Aims / A. Knowledge / 2. Understanding ]

Full Idea

Mediaeval logicians had a principle, 'Eadem est scientia oppositorum': in order to attain a clear conception of what it is for A to be the case, one needs to attain a conception of what it is for A not to be the case.

Gist of Idea

Medieval logicians said understanding A also involved understanding not-A

Source

Ian Rumfitt (The Boundary Stones of Thought [2015], 7.2)

Book Reference

Rumfitt,Ian: 'The Boundary Stones of Thought' [OUP 2015], p.196


A Reaction

Presumably 'understanding' has to be a fairly comprehensive grasp of the matter, so understanding the negation sounds like a reasonable requirement for the real thing.