 In an analogous way, a language can be identified with the set of all and only its expressions (regardless of what sort of object an expression is: a word sequence, a tree structure, a complete derivation, or whatever), which is the extensional view; but it can also be identified intensionally by means of a recipe or formal specification of some kind—what linguists call a grammar. Ludlow (2011) considers the first I (individual) to be the weakest link and thus the most expendable. He argues in its stead for a concept of a “\(\Psi\)-language” which allows for the possibility of the I-language relating to external objects either constitutively or otherwise. 