Since it seems pretty obvious that not everybody knows what it means to support assertions with evidence, I thought we could describe the process by which assertions are made and what constitutes support for an assertion.
Assertions are when you make claims that something exists or is a certain way. I'll go step by step through supporting (or not supporting) a simple claim with various levels of evidence appropriate for the discussions we have here.
There's the claim: Death Valley is the lowest elevation in North America.
Now, normally that's a statement so non-contentious that we allow it to pass without comment. But it is felt that posters should be at least ready to substantiate
all claims if asked to do so, so let's try and support it.
1) Death valley is the lowest elevation in North America because it's lower than all other elevations in North America.
Obviously this isn't support for the claim, it's just restating the claim in another way. Trying to support a claim with itself is circular reasoning.
2) Death valley is the lowest elevation in North America because it's been measured to be the lowest.
Better, but measured by who? You? Measured when? Measured how? Which locations were measured? "Measured to be lowest" is still a claim that needs to be itself supported. Making more unsupported claims doesn't support anything.
3) Death valley is the lowest because the
CIA World Factbook says so.
Still better, but something can still be just a claim even if it's somebody else making it. Why does the CIA conclude that Death Valley is the lowest? They don't say, and let's keep in mind that the CIA is not infallible, as I hear some Iraqis discovered recently.
4) Death valley is the lowest elevation according to maps from the
US Geologic Survey. The maps list their date of compliation and presumably you could contact the USGS personel if you wanted to know specifically when the surveys were performed on-site.
That's support for the claim. The evidence is trustable, verifiable, peer-reviewed, and accessable.
Man, it took me a long time to try to find some of that, which goes to show another reason we don't demand evidence except for the most contentious claims - the more widely something is known, the less anybody bothers to make references to it.
Maybe that'll give people some idea about the burden of proof at this forum. You don't have to go as far as I did - the CIA Factbook cite would probably have been sufficient - but you at least have to get a reasonable, relevant cite for your contentious assertions, or be prepared to admit you can't support them.
I've tried to keep it simple so I'm sure there's much to debate on the subject. I welcome any thoughts, especially from folks a little more used to supplying evidence than I usually am.
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