Praesidium

Tuesday, November 15, 2011

Ps and Qs (Reposted)

I tried this before, but didn't get any comments - perhaps because I think there was some Facebook problem at the time (posts here are imported onto Facebook and I get most of my comments that way) - so I thought I'd try again...

Something I've just been thinking about and want a second opinion on. (It's not anything I'm working on, just a thought sparked by something I was reading.)

Suppose we have two propositions, P and Q. P is true. Q is a more extreme version of P. Does it follow that Q is false? Or that we have reason to believe P rather than Q?

I think much depends on the content of these propositions and the way in which Q is more extreme than P. For instance:

P: Abortion is usually wrong.
Q: Abortion is always wrong.

Here P allows (though does not logically imply) that some abortions are not wrong, which Q doesn't. If it's the case that some abortions are permissible, then Q is false and we have reason not to believe it.

But one problem is that P, while true, might be under inclusive. For instance:

P: Abortion is always wrong after 30 weeks.
Q: Abortion is always wrong after 28 weeks.

Stipulate that Q is true. Then it follows that P is true also, because P is weaker. That Q is more extreme than P does not make it false, because it is true (by stipulation), even though P is also true. Someone who believes P believes truly, but they also have reason to adopt the more extreme position Q. (Because P is true, but not the whole truth.)

I think this counter example works, but it depends of course on P not being the whole truth. I'm wondering if there are other counter examples. I suspect, perhaps, there may be some in which the way that Q is more extreme than P is practically irrelevant. These would seem, at least, cases where though Q is actually less correct, there is no harm in moving from the correct belief P to the not entirely correct belief Q, given that Q entails P.

Thoughts and comments welcome...

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