Full Idea
If the Mentalese story about the content of thought is true, then there couldn't be a Private Language Argument. Good. That explains why there isn't one.
Gist of Idea
The theory of the content of thought as 'Mentalese' explains why the Private Language Argument doesn't work
Source
Jerry A. Fodor (In a Critical Condition [2000], Ch. 6)
Book Reference
Fodor,Jerry A.: 'In Critical Condition' [MIT 2000], p.68
A Reaction
Presumably Mentalese implies that all language is, in the first instance, intrinsically private. Dogs, for example, need Mentalese, since they self-evidently think.