The idea of the 'Marketplace of Ideas' comes from John Stuart Mill, in his classic defence of free speech "On Liberty", 1859. In 'On Liberty', he writes: "He who knows only his own side of the case knows little of that. His reasons may be good, and no one may have been able to refute them. But if he is equally unable to refute the reasons on the opposite side, if he does not so much as know what they are, he has no ground for preferring either opinion... Nor is it enough that he should hear the opinions of adversaries from his own teachers, presented as they state them, and accompanied by what they offer as refutations. He must be able to hear them from persons who actually believe them...he must know them in their most plausible and persuasive form.” The core idea of the 'marketplace of ideas' is that truth will eventually replace error in a fair contest of thought. History bears that out in some areas - science, for example, where there is such a thing as objective truth. But there's a political sense in which the Marketplace of Ideas works - that it is in debate, through argument, in the 'marketplace' that we build our best political selves. A society in which all ideas can be traded is free, and is ultimately happier and healthier than its alternatives.

Any debate without some form of structure or moderation or impartial 3rd party judgement will be won by the person with the prettiest face, the loudest voice, and the most convincing lies, if your opponent lies and you are the only person who cares whether or not that statement is true, how do you continue the debate? And why would the audience of this debate believe you?

The "marketplace of ideas" works but in a counter-intuitive way. Maybe not as Dave Rubin wants it to, but it works.