Larry Summers, the former Treasury Secretary, appeared Wednesday morning on CNBC, and he laid into Donald Trump’s economic program. Trump’s proposed tax cuts don’t make sense, Summers said, because they would target very high earners, meaning that a lot of the money they free up could end up being saved, rather than spent. And Trump’s infrastructure plans are questionable, Summers argued, because in at least one version of the plans, they depend largely on private financing. The problem, Summers said, is that pension funds and other big investors won’t invest in essential tasks like repairing the nation’s roads, bridges, and airports, because projects like those don’t produce any revenues. So where would the financing for them come from?