Abstract: The unification of the paradoxes of truth and vagueness has been a topic of recurrent philosophical interest (e.g. McGee 1989/1990, Tappenden 1993, Field 2003/2008, Priest 1994/2010). I will present a sequence of observations which illustrate how the liar and sorites paradoxes are formally related, culminating in the observation that both give rise to similar sorts of mathematical incompleteness phenomena. On this basis, I will highlight the possibility of using formal undecidability in modeling semantic indeterminacy.