Full Idea
In classical logic definitions are thought of as revealing our attempts to refer to objects, ...but for intuitionist or constructivist logics, if our definitions do not uniquely characterize an object, we are not entitled to discuss the object.
Gist of Idea
Classical definitions attempt to refer, but intuitionist/constructivist definitions actually create objects
Source
Michèle Friend (Introducing the Philosophy of Mathematics [2007], 2.4)
Book Reference
Friend,Michèle: 'Introducing the Philosophy of Mathematics' [Acumen 2007], p.36
A Reaction
In defining a chess piece we are obviously creating. In defining a 'tree' we are trying to respond to fact, but the borderlines are vague. Philosophical life would be easier if we were allowed a mixture of creation and fact - so let's have that.