Content externalism without thought experiments?

A recent argument against content internalism bucks tradition: it abandons Twin-Earth-style thought experiments and instead claims that internalism is inconsistent with plausible principles relating belief contents and truth values. Call this the transparency argument. Here, it is shown that there is a structurally parallel argument against content internalism’s foil: content externalism. Preserving the transparency argument while fending off the parallel argument against externalism requires that content-determination and truth-value-determination are implausibly linked together and that eternalism about belief contents is true. Given these requirements, there may be reason to prefer simple, thought-experiment-based arguments against internalism – the sort of arguments that the transparency argument is meant to supersede.