Theory, Model, Method
To make intuitions about linguistic structures more reliable they are often derived as results from specific tests (also see Experimental linguistics). Typical syntactic tests concern the hierarchical structure or constituency of sentences (cf. 'syntax'), the ambiguity of sentences or words, etc.
However, both personal intuitions and elicited non-linguists’ judgments are realisations of the mental and underlying (non-observable) competence of native speakers and depend on introspection. The method is evidently deductive.
One problem still remains: the reliance on speakers’ intuitions. Among other things, this presupposes that speakers’ judgments correlate with the actual language behaviour and that speakers do not err or are at least mistaken in their personal perception of linguistic objects.