I STILL don't understand necessary vs sufficient assumptions

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Joined: Wed Jun 12, 2013 5:45 am

Re: I STILL don't understand necessary vs sufficient assumptions

Postby Reframe » Wed Jun 12, 2013 10:21 pm

vuthy wrote:Interesting. So would it be fair to think (at least for now as I get my footing) of necessary as something like "bare minimum," or sine qua non? In other words, a necessary assumption is a kind of minimum threshold thing -- something without which the conclusion can't be true. Take it away and it doesn't matter what else is out there in the world -- the conclusion can't happen. Keep it in, and the conclusion has at least a fighting chance of being true.

If this is roughly right, I feel better about it -- although I do go back to the fact that much of the confusion comes from the word "necessary," which we tend to associate with being a strong descriptive (e.g., "by any means necessary"). Whereas in conditional logic, it's almost another meaning of necessary that prevails -- something like I described above.

This sounds right. Another way to think about it is that, although in one sense a NA question is a kind of assumption question, in another sense it's a kind of inference question: it asks for something that must be true given the prompt.

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