Washington ? Noting that people “criticize me for harping on the obvious,” Calvin Coolidge justified that practice by saying, “If all the folks in the United States would do the few simple things they know they ought to do, most of our big problems would take care of themselves.” Consider what individual Americans know they ought to do, and what their government should know not to do.

The nation could subtract from its health care bill a significant portion of the costs caused by violence, vehicular accidents, AIDS, coronary artery disease, lung cancer and Type II diabetes resulting from obesity. All six problems are significantly related to known risky behavior, which can change.

Visa, the credit card company, recently reported a behavioral change that went remarkably unremarked: In the fourth quarter of 2008, for the first time ever, the dollar volume of purchases made with its debit cards — they deduct funds immediately from checking accounts, rather than allowing card users to carry debt — exceeded the dollar volume of its credit card transactions.

Suppose Americans begin living within their means. Will this marvel complicate the nation’s biggest domestic challenge, the task of achieving and sustaining the rapid economic growth necessary for generating revenues to fund pension and medical entitlements for an aging population?

The nation now is 17 months into the demographic deluge that began in January 2008 when the leading edge of the wave of 78 million baby boomers began exercising the preposterous entitlement to collect Social Security at age 62, as most Social Security recipients do. In 1935, when Social Security was enacted, no one envisioned it supporting most retirees for a third of their adult lives. So, should Americans shop until the boomers drop?

During recent periods of strong growth, 70 percent of economic activity has been personal consumption. If Americans’ new sobriety — more saving, less spending — survives the first tantalizing green shoots of recovery, can the recovery continue? It will not be killed by moderate thrift, because money saved does not disappear under mattresses; much of it goes into institutions that put it to work. The personal savings rate rose to 5.7 percent in April, the highest since 1995. It was 9 percent during the 1980s boom.

The world economy’s condition is so weak that this year global consumption of electricity will decline for the first time since 1945. Using a defibrillator as large as the sum of money being thrown at the U.S. economy will somewhat quicken its pulse. But a patient cannot become healthy attached to a defibrillator. If the economy relapses, three causes might be: protectionism, refusal to allow creative destruction, and rising long-term interest rates.

The Smoot-Hawley tariff of 1930 ignited reciprocal protectionism that suffocated global trade and deepened the Depression. The cap-and-trade legislation passed recently by a House committee is Smoot-Hawley in drag: It contains provisions for tariffs on imports designated “carbon-intensive” — goods manufactured under less carbon-restrictive rules than those of the proposed U.S. cap-and-trade regime. Eco-protectionism is a recipe for reciprocity.

The administration’s deepening involvement in designing and marketing automobiles through two crippled companies ignores this truth: Capitalism is a profit and loss system, and the creative destruction it produces is supposed to clear away failures like Chrysler, freeing up capital for more productive uses.

Recently, Standard and Poor’s noted that Britain’s ballooning need to borrow might cost the country its AAA credit rating, which would raise its cost of borrowing. Britain’s deficit this year is expected to be at least 12.4 percent of GDP. America’s is scheduled to be more than 13 percent. Years of such government borrowing might crowd private sector borrowers out of credit markets and raise long-term interest rates.

Trillions of dollars of capital are being allocated sub-optimally, by politically tainted government calculations rather than by the economic rationality of markets. Hence the nation’s prospects for long-term robust growth — and for funding its teetering architecture of entitlements — are rapidly diminishing.

The president’s astonishing risk-taking satisfies the yearning of a presidency-fixated nation for a great man to solve its problems. But as Coolidge said, “It is a great advantage to a president, and a major source of safety to the country, for him to know that he is not a great man.” What the country needs today in order to shrink its problems is not presidential greatness. Rather, it needs individuals to do what they know they ought to do, and government to stop doing what it should know causes or prolongs problems.

— George Will is a columnist for Washington Post Writers Group.