Linguist: Only if a sentence can be diagrammed is it grammatical. Any grammatical sentence is recognized as grammatical by speakers of its language. Speaker X' s sentence can be diagrammed. So, speaker X' s sentence will be recognized as grammatical by speakers of its language. The linguist's reasoning is flawed because it fails to consider the possibility that ['some ungrammatical sentences are diagrammable', 'all grammatical sentences can be diagrammed', 'some ungrammatical sentences are recognized as ungrammatical', 'most people are unable to diagram sentences correctly']