Lies, lies, lies …
Crucial for Davidson’s account of radical interpretation is that although we can distinguish verbal from non-verbal behaviour, we cannot separate them. The perennial liar can be found out because what we say is linked to what we do and because what we do is to some extent ‘shared beyond our will’ (i.e., we cannot determine that at will). That some instance of verbal behaviour is a lie will then be revealed by some particular instance of non-verbal behaviour being incongruent with ours where ‘by assumption’ it should be the same. If a perennial liar were able to completely separate their verbal from their non-verbal behaviour, and hence be congruent in what they do, yet lie in what they say, they could indeed not be found out.