 Now as it's formulated here, this argument doesn't rule out the view that ‘that’-clauses refer to mentalese sentence types, but the argument can be extended to rule out that view as well (e.g., one might do this by talking not of an American and a Russian but of two creatures with different internal languages of thought). I won't run through the details of this here, since, as we've seen, anti-platonists can't claim that ‘that’-clauses refer to types anyway, because types are abstract objects. But if we assume that that version of the argument is cogent as well, then it follows that ‘that’-clauses don't refer to sentences of any kind at all and, hence, that they must refer to  propositions.[9]