If you find your interlocutor's position ambiguous in some major way, then you should, firstly, tell them, and secondly, ask them to explain. Otherwise confusio

If you find your interlocutor's position ambiguous in some major way, then you should, firstly, tell them, and secondly, ask them to explain. Otherwise confusion may ensue as to what exactly is being argued for and against. If the ambiguity is incidental, then the principle of charity is not really doing much. I take it that your example - about a phrase admitting a valid and invalid inference - is of this kind. Though I do agree that we shouldn't jump upon those kinds of slippages. If you read carefully and allow the conversation to unfold, while prompting your interlocutor to explain what remains unclear to you, then generally you can get a fairly accurate impression of their views. More often than not, the problem is not ambiguity, but an unwillingness to listen, and engage thoughtfully with others, through a genuine dialogue.