THE STRONG AND THE WEAK WHORFIAN HYPOTHESIS. It seems that much of the “fierce debate” on whether language can shape the thoughts of those who speak it turns on disagreement about a strong and a weak form of the hypothesis. The blogonlinguistics site explains here: “The theory of linguistic relativity is known in two versions: the strong hypothesis (= linguistic determinism) and the weak hypothesis. It is necessary to clarify that the words “strong” and “weak” are not related to the strength of the scholarly argumentation, but rather to the degree to which language is assumed to influence our thought and behaviour. According to the strong version, the language we speak determines/constraints the way we think and view the real world. According to the weak version, the language does influence in some way the way we think and view the real world, however, does not fully determine or constraint it.”
Ken Arneson is applying the weak form of the hypothesis. Because Swedish makes “clear distinctions” between belief in an opinion and belief in a fact (tycka and tro), a Swedish speaker has to distinguish which kind of belief he has every time he has to choose between the two words. Their language makes Swedes proficient in making the distinction. The strong form of the hypothesis would argue that English speakers cannot make the distinction at all, which is obviously untrue. It is just more difficult to make the distinction in English.