Is radical interpretation possible

Argument form T 1. No language would be interpretable at all unless it were radically interpretable;2 that is, unless it were interpretable from the epistemic position of a radical interpreter. 2. No language would be radically interpretable unless it were F.3 3. (Natural) languages are actually interpreted (for example, by children who learn them and field linguists who translate them); hence, natural languages are radically interpretable. 4. Therefore, natural languages are F.4