Full Idea
There is a crucial distinction in term logic between affirming a negated predicate term of some subject and denying the unnegated version of that term of that same subject. We must distinguish 'X is non-P' from 'X is not P'.
Gist of Idea
Negating a predicate term and denying its unnegated version are quite different
Source
George Engelbretsen (Trees, Terms and Truth [2005], 2)
Book Reference
'The Old New Logic', ed/tr. Oderberg,David S. [MIT 2005], p.32
A Reaction
The first one affirms something about X, but the second one just blocks off a possible description of X. 'X is non-harmful' and 'X is not harmful' - if X had ceased to exist, the second would be appropriate and the first wouldn't? I'm guessing.
Related Ideas
Idea 18903 Sommers promotes the old idea that negation basically refers to terms [Sommers, by Engelbretsen]
Idea 18904 'Predicable' terms come in charged pairs, with one the negation of the other [Sommers, by Engelbretsen]