Putnam originally developed his causal theory of meaning in order to support scientific realism and reject the notion of incommensurability. Later he gave up this position and adopted instead what he called ‘internal realism’, but apparently without changing his mind on topics related to his former philosophy of language. The question must arise whether internal realism, which actually is a species of antirealism, is compatible with the causal theory of meaning. In giving an answer I begin with an analysis of (...) the content and metaphysical background of scientific realism. I show that it presupposes metaphysical realism and that Putnam's philosophical conversion is due to his becoming aware of the latter's incoherence. After giving a brief sketch of internal realism I conclude by arguing that within this new theoretical framework the causal theory of meaning loses its force as a weapon against incommensurability. (shrink)