> You can have a free market where this isn't even approximately true, of course, but the farther it is from true, the weaker the argument for the desirability of free markets is.
That's debatable. In some markets (Veblen/Giffen goods, goods with a price elasticity that approaches zero, etc.) you could say that information doesn't matter because price is irrelevant, but I personally would say that you don't have a free market or any approximation of such without at least reasonable information. Which, you know, is up for interpretation.
I think there is a semantic issue where some people use free markets to mean markets run by mutual exchange by agreement between participants, and see the conditions that make such markets efficient as separate factors which may or may not be present, and other who use “free market” to include the combination of voluntary exchange with some or all of the conditions that make such exchange efficient.
That's debatable. In some markets (Veblen/Giffen goods, goods with a price elasticity that approaches zero, etc.) you could say that information doesn't matter because price is irrelevant, but I personally would say that you don't have a free market or any approximation of such without at least reasonable information. Which, you know, is up for interpretation.