According to Quine, the indeterminacy of translation shows that there are no criteria of identity for meanings, and hence that our intuitive notion of meaning is vacuous (PL 1–2, 67–8; OR 23; PT 37, 52–3). This in turn spells ruin not just for analyticity, but for intensional notions (proposition, attribute, necessity, etc.) in general. It also undermines the ‘traditional semantics’ which revolved around these notions. Quine variously characterizes this semantics as ‘mentalistic’, on account of its commitment to meaning as something beyond behaviour, as ‘absolutist’, on account of its presupposing separate and distinct meanings, and as ‘introspective’, on account of its uncritical acceptance of our intuitive notion of meaning (RR 36; MVD 86; RHS 493; ITA 9).

Indeterminacy also threatens the idea that propositional attitudes have a determinate content. What we believe and desire is expressed by sentences. If it is pointless to ask whether a sentence the native assents to means ‘p’ or ‘q’, it is also pointless to ask whether she believes that p or that q (RIT 180–1). Since beliefs and desires are individuated by their content, this will demolish what is known as ‘intentional psychology’, our pervasive practice of explaining the behaviour of human beings by reference to their beliefs and desires. Quine has welcomed this consequence. He accepts the ‘Brentano thesis’, according to which our intentional and intensional statements cannot be reduced to the purely extensional statements of the physical sciences.