I recently read an interesting essay by Peter Earle of the American Institute for Economic Research. The essay revolved around a question that supposedly no libertarian had ever been able to answer: What would keep someone from buying a massage table, a set of steak knives, and with no training whatsoever starting a surgical practice?
Mr. Earle's essay is a fascinating overview of libertarian and economic thought, with defenses of the usual regulatory practices that modern libertarian thought tends to embrace as necessary. What is especially fascinating is that he never actually answered the question as it had been posed to him. but rather seemed more interested in establishing why such a question was not germane to libertarian thought.
The answer, of course, is supremely obvious: "Nothing at all."