 Given the tension with SK, why should we accept EXT in the first place? One reason is that EXT is more or less entailed by many contemporary theories of content. For instance, several theories say (in short) that a  concept[5]  has its content in virtue of certain causal relations the concept bears to an environmental referent (Dretske 1981, Millikan 1984; 1989, Fodor 1987; 1990; also, cf. Kripke 1972 and Evans 1982, ch. 6). Others see mental content as posited when interpreting a subject vis-à-vis objects in her environment (Davidson 1973; 1987, Dennett 1975). Still others see content as determined by the inferences that feature the relevant concept. Such an inference, moreover, is often defined partly by the environmental object which normally prompts the inference, or in which the inference normally terminates (Sellars 1954).