You don't think they might be a bit, um... biased? :-)
Possibly. I linked them because they're convenient. I know enough economics that index funds being optimal for investors without special knowledge is obvious to me; you can find more on wikipedia or Motley Fool.
let me ask you, which market? There are a whole bunch of different markets -- what makes large-cap US equity special?
I personally recommend VTSMX for investors in the US, because there are a handful of reasons to prefer investing in domestic funds (especially if you live in the US). There is advice out there targeted at low-load funds if you're interested in putting more thought into the choice. If you live elsewhere, there may be tax considerations that make other funds superior (google 'index fund [your country]', and you should probably find some useful advice), but if you live in a particularly small country investing only in domestic stocks will probably increase your volatility significantly over an American only investing in US stocks.
I know enough economics that index funds being optimal for investors without special knowledge is obvious to me
I suspect I know more economics than you and that optimality is not obvious to me at all.
Let me ask you again the question which you sidestepped -- which market? An "index fund" is a shortcut for "passively managed diversified portfolio" and that's a very large territory.
Let's even assume market efficiency. First, investors are different. Let's take a few: a 25-year-old grad student in Singapore with $5,000; a 65-year old Ca...
P/S/A: There are single sentences which can create life-changing amounts of difference.