Full Idea
A logically perfect language should satisfy the conditions that every expression grammatically well constructed as a proper name out of signs already introduced shall in fact designate an object.
Gist of Idea
In a logically perfect language every well-formed proper name designates an object
Source
Gottlob Frege (On Sense and Reference [1892], p.41)
Book Reference
Frege,Gottlob: 'Translations from the Writings of Gottlob Frege', ed/tr. Geach,P/Black,M [Blackwell 1980], p.70
A Reaction
This seems to cramp your powers of reasoning, if you must know the object to use the name ('Jack the Ripper'), and reasoning halts once you deny the object's existence ('Pegasus'), or you don't know if names co-refer ('Hesperus/Phosphorus').