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Full Idea
In intuitionist logic each connective has one introduction and one elimination rule attached to it, but in the classical system we have to add an extra rule for negation.
Gist of Idea
Intuitionism as natural deduction has no rule for negation
Source
Edwin D. Mares (Negation [2014], 5.5)
Book Ref
'Bloomsbury Companion to Philosophical Logic', ed/tr. Horsten,L/Pettigrew,R [Bloomsbury 2014], p.202
A Reaction
How very intriguing. Mares says there are other ways to achieve classical logic, but they all seem rather cumbersome.
Related Idea
Idea 18789 Intuitionist logic looks best as natural deduction [Mares]