§82

"What do I call 'the rule according to which he proceeds'? - The hypothesis that satisfactorily describes his use of words, which we observe..."
I assume the answer Wittgenstein would want to give to this would be 'no'. A rule is not a hypothesis - not the kind of thing that might be tested. However, it presumably does make sense to talk about gleaning rules from observed behaviour. You might get to grips with the rules of chess by observing people playing and correcting each other.