(Bloomberg View) -- The Republican vow tosignificantly reduce the size of government is a foolish pipedream, Larry Summers says, not because of liberal policyaspirations but because of structural economic realities.

At a lunch on Wednesday, Summers, a former Treasury secretaryand a leading Democratic economic-policy thinker, explained thesubstantive as well as political impracticalities of cuttingentitlements and defense spending in the years ahead.

"If we want to maintain traditional American values, governmentwill need to be significantly larger," Summers declared at theevent, hosted by the liberal Center on Budget and PolicyPriorities.

What’s needed now, he said, is tax reform modeled on the law enacted in 1986that improves the tax code and doesn’t lose money.

What we can't afford, the economist declared, is a tax cut likethe one in 1981 that drained billions of dollars from the Treasury.As the plans of the Trump administration and congressionalRepublicans unfold, it becomes clearer that they are closer to the1981 approach.

Summers, who was director of the National Economic Council underPresident Barack Obama, denigrated those efforts and summarizedfour economic realities that undercut the possibility of downsizinggovernment:

The aging population. As people livelonger, government programs have more claims on them, so ifentitlements are maintained at current levels or even cut slightly,government spending will increase.

The unsustainable, dramatic rise ininequality. A role of government, henoted, is to address and "ameliorate" inequality.

Changes in structural pricing that disproportionately affectgovernment. As an example, Summers said, pegging the 1983consumer price index at $100, the cost of a television today would$6, while the cost of a day in the hospital, or a year in college,would be $600. The price of televisions, he noted, doesn’t muchaffect government spending; hospital prices and college costsdo.

Rising national securitycosts. Summers noted that the three major countries thatcould be seen as potential American adversaries -- China, Russiaand Iran -- are all increasing military spending at rapid rates. Itis unrealistic to think that won't affect American policy, despitethe wishes of many political liberals who hoped government couldraise revenue from defense cuts. “To view the Pentagon as a cashcow is a grave and serious mistake,” Summers said.

He criticized the emerging Republican tax plans ascounterproductive for the economy and for long-term governmentrevenues.

Most Republicans, although giving lip service to major reforms,are focused on a huge tax cut for corporations and higher-incomeindividuals.

Noting the relatively low cost of capital, with low interestrates, and the need to bolster revenues in the years ahead, hesaid: "This is not the moment for net tax cuts."

Summers argued that a real tax reform, like the 1986 plan workedout between Republican President Ronald Reagan and a politicallydivided Congress, would be beneficial.

Rates could be cut by slashing tax preferences like the carriedinterest enjoyed by some private-equity and hedge-fund executivesand the huge real-estate tax breaks, among others, and by devotingmore resources to tax compliance and enforcement.

The economist didn't seem averse to a modest cut in thecorporate tax rate but was appalled by Republican arguments to cutthis top rate from 35 percent to as low as 15 percent.

"That might be a good thing for my finances, but it would beoutrageous public policy," said Summers, who is in demand as aspeaker and consultant.

He ridiculed the populist-sounding arguments of Trump adviserGary Cohn and Treasury Secretary Steven Mnuchin, who say, forexample, that tax cuts would help firemen since a resulting surgein stocks would help their retirement plans. Most firemen havedefined-benefit pension plans that wouldn't be affected, Summersnoted.

At the lunch, the Center on Budget and Policy Prioritiesreleased its own projections for federal spending and revenues. By2035, with reasonably modest assumptions, spending would increaseto 23.5 percent of the gross domestic product from 20.9 percent.Thus, the center contends, it will be necessary for revenue growthto keep pace -- or the result would be a massive increase indeficits and debt.

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