WASHINGTON -- Authoritarianism, always latent in progressivism, is becoming explicit. Progressivism's determination to regulate thought by regulating speech is apparent in the campaign by 20 state attorneys general, none Republican, to criminalize skepticism about the supposedly "settled" conclusions of climate science. Four core tenets of progressivism are: First, history has a destination. Second, progressives uniquely discern it. (Barack Obama frequently declares things to be on or opposed to "the right side of history.") Third, politics should be democratic but peripheral to governance, which is the responsibility of experts scientifically administering the regulatory state. Fourth, enlightened progressives should enforce limits on speech (witness IRS suppression of conservative advocacy groups) in order to prevent thinking unhelpful to history's progressive unfolding. Progressivism is already enforced on campuses by restrictions on speech that might produce what progressives consider retrograde intellectual diversity. Now, from the so-called party of science, aka Democrats, comes a campaign to criminalize debate about science. "The debate is settled," says Obama. "Climate change is a fact." Indeed. The epithet "climate change deniers," obviously coined to stigmatize skeptics as akin to Holocaust deniers, is designed to obscure something obvious: Of course the climate is changing; it never is not changing -- neither before nor after the Medieval Warm Period (end of the 9th century to the 13th) and the Little Ice Age (1640s to 1690s), neither of which was caused by fossil fuels. Today, debatable questions include: To what extent is human activity contributing to climate change? Are climate change models, many of which have generated projections refuted by events, suddenly reliable enough to predict the trajectory of change? Is change necessarily ominous because today's climate is necessarily optimum? Are the costs, in money expended and freedom curtailed, of combating climate change less than the cost of adapting to it? But these questions may not forever be debatable. The initial target of Democratic "scientific" silencers is ExxonMobil, which they hope to demonstrate misled investors and the public about climate change. There is, however, no limiting principle to restrain unprincipled people from punishing research entities, advocacy groups and individuals. But it is difficult to establish what constitutes culpable "misleading" about climate science, of which a 2001 National Academy of Sciences report says: "Because there is considerable uncertainty in current understanding of how the climate system varies naturally and reacts to emissions of greenhouse gases and aerosols, current estimates of the magnitude of future warming should be regarded as tentative and subject to future adjustments (either upward or downward)." Did Al Gore "mislead" when he said seven years ago that computer modeling projected the Arctic to be ice-free during the summer in as few as five years? A 21st attorney general, of the Virgin Islands (where ExxonMobil has no business operations or assets), accuses the company with criminal misrepresentation regarding climate change. This, even though before the U.S. government in 2009 first issued an endangerment finding regarding greenhouse gases, ExxonMobil favored a carbon tax to mitigate climate consequences of those gases. This grandstanding attorney general's contribution to today's gangster government is the use of law enforcement tools to pursue political goals -- wielding prosecutorial weapons to chill debate, including subpoenaing private donor information from the Competitive Enterprise Institute, a Washington think tank. The party of science, busy protecting science from scrutiny, has forgotten Karl Popper (1902-1994), the philosopher whose "The Open Society and Its Enemies" warned against people incapable of distinguishing between certainty and certitude. In his essay "Science as Falsification," Popper explains why "the criterion of a scientific status of a theory is its falsifiability, or refutability, or testability." America's party of science seems eager to insulate its scientific theories from the possibility of refutation. The leader of the attorneys general, New York's Eric Schneiderman, dismisses those who disagree with him as "morally vacant." His moral content is apparent in his campaign to ban fantasy sports gambling because it competes with the gambling (state lottery, casinos, off-track betting) that enriches his government. Then there is Sen. Sheldon Whitehouse, D-R.I., who suggests using the Racketeer Influenced and Corrupt Organizations Act, written to fight organized crime, to criminalize what he calls the fossil fuel industry's "climate denial apparatus." The Justice Department, which has abetted the IRS cover-up of its criminal activity, has referred this idea to the FBI. These garden-variety authoritarians are eager to regulate us into conformity with the "settled" consensus du jour, whatever it is. But they are progressives, so it is for our own good. George Will's email address is firstname.lastname@example.org.