There is a growing belief among mortgage investors, industry groups and some policymakers in Washington that some type of explicit government guarantees for mortgage lending will be necessary to undergird a new housing finance system in America. Yet whether by the sale of insurance on mortgage-backed securities or a public utility model replacing Fannie Mae and Freddie Mac with new government-sponsored enterprises, this would be a tragic mistake, repeating the errors of history, and putting taxpayers and the housing industry itself at risk. This policy summary offers ten arguments for why there should be no government role—explicit or implicit—in guaranteeing housing finance.