 We now turn to some realist responses to these challenges. The Manifestation and Language Acquisition arguments allege there is nothing in an agent’s cognitive or linguistic behaviour that could provide evidence that s/he had grasped what it is for a sentence to be true in the realist’s sense of ‘true’. How can you manifest a grasp of a notion which can apply or fail to apply without you being able to tell which? How could you ever learn to use such a concept?