In September, a pundit fight broke out over whether Team Blue or Team Red is more "anti-science." Microbiologist Alex Berezow, editor of RealClearScience, struck the first blow in the pages of USA Today. "For every anti- science Republican that exists," he wrote, "there is at least one anti-science Democrat. Neither party has a monopoly on scientific illiteracy."

Then Chris Mooney, author of The Republican War on Science, denounced Berezow's column as "classic false equivalence on political abuse of science" over at the Center for American Progress's Climate Progress blog. Mooney accused Berezow of trying "to show that liberals do the same thing" by "finding a few relatively fringe things that some progressives cling to that might be labeled anti-scientific."

Berezow acknowledged that many prominent Republican politicians, including several presidential candidates, deny biological evolution, are skeptical of the scientific consensus on man-made global warming, and oppose research using human embryonic stem cells. Democrats, Berezow argued, tend to be more anti-vaccine, anti-nuclear power, anti-biotechnology, and anti-biomedical research involving tests on animals.

In support of these claims Berezow cited polling data from a 2008 survey conducted by the Pew Research Center for the People and the Press, which identified a number of partisan divides on scientific questions. On biological evolution, the survey reported that 97 percent of scientists agree that living things, including human beings, evolved over time, compared to 58 percent of Democrats and 49 percent of Republicans.

On climate change, the Pew survey reported that 84 percent of scientists believe that recent warming is the result of human activity, compared to 64 percent of Democrats and only 30 percent of Republicans. That's a truly deep divide on a scientific issue.

The Pew survey next asked about federal funding for human embryonic stem cell research, which Democrats favored by 71 percent compared to only 38 percent for Republicans. But the GOP response is likely tied to two issues: (1) the belief that embryos have the same moral status as adult people; and (2) the general belief that spending taxpayer dollars on research is suboptimal. These are policy differences rather than scientific differences.

But what about Berezow's examples of left-wing bias? Mooney's basic assertion is that Democratic anti-science is a fringe with no power, unlike the know-nothing Tea Party activists who influence Republican politics. For example, Mooney argues that People for the Ethical Treatment of Animals "is not a liberal group commanding wide assent for its views on the left, doesn't drive mainstream Democratic policy, etc." Fair enough. But the Pew survey does report that 48 percent of Democrats oppose using animals in scientific research, whereas only 33 percent of Republicans do. Like stem cells, using animals in research is often framed as a moral issue.

With regard to nukes, the Pew survey found that 70 percent of scientists are in favor of building more nuclear power plants, compared to 62 percent of Republicans and just 45 percent of Democrats. This difference reflects divergent views on nuclear safety: A 2009 Gallup poll reported that while 73 percent of Republicans are confident in the safety of nuclear power plants, only 46 percent of Democrats agree.

What about partisan attitudes toward genetically enhanced crops and animals? A 2006 survey by the Pew Trusts found that 48 percent of Republicans believe that biotech foods are safe compared to 42 percent of Democrats. Are they right to be leery? A 2004 National Academy of Sciences report noted: "To date, no adverse health effects attributed to genetic engineering have been documented in the human population." That is still the case today.

Mooney agrees that "there is some progressive resistance and some misuse of science in this area," but insists that "it is not a mainstream position." However, that only holds true if groups opposing biotech foods—such as the Sierra Club, the Consumers Union, and Greenpeace—can be considered to be on the fringe of Democratic Party politics.

What about vaccines? Berezow mentions data showing that vaccine refusals are highest in notoriously Blue states like Washington, Vermont, and Oregon. In fact, the vaccine/autism scare was fueled in part by prominent lefties like Robert F. Kennedy Jr., writing in popular publications such as Rolling Stone and Salon. In addition, such non-fringy characters as then-Sen. Barack Obama (D-Ill.) have declared things like, "We've seen just a skyrocketing autism rate. Some people are suspicious that it's connected to the vaccines. This person included. The science right now is inconclusive, but we have to research it." Sen. John McCain (R-Ariz.) has made similar statements.

By the way, the Pew poll found that 71 percent of both Republicans and Democrats support mandating childhood vaccination.

Expanding on his argument at DeSmogBlog, Mooney asserts that the left doesn't abuse science; it merely has policy disagreements about it. As an example, he cites affection for the precautionary principle. "There is always much scientific uncertainty, and industry claims it's safe, but environmentalists always want to be more cautious—e.g., adopting the precautionary principle," he notes, adding: "The precautionary principle is not an anti-science view, it is a policy view about how to minimize risk."

But as University of Chicago law professor and current administrator of the White House Office Information and Regulatory Affairs Cass Sunstein noted in a 2003 working paper entitled "Beyond the Precautionary Principle," this idea "imposes a burden of proof on those who create potential risks, and it requires regulation of activities even if it cannot be shown that those activities are likely to produce significant harms." Note specifically the latter point.

Furthermore, Sunstein observed, the precautionary principle is now pervasive, applying to global warming, nuclear power, pesticides, and biotech crops. Restraint on experimentation is unscientific in the sense that it demands the impossible: Researchers can never show in advance that any technological or scientific activity will never produce significant harm.

In addition, law professor Dan Kahan and his colleagues at the Yale Cultural Cognition Project have shown that the strong urge to avoid scientific and technological risk is far more characteristic of people who have egalitarian and communitarian values, that is to say, left-leaning folks.

Everybody has values that they are anxious to protect and everybody, including liberals (and libertarians!), struggles with confirmation bias. The operation of the scientific process is the only effective way humanity has devised for overcoming bias and figuring out reality. In most cases the scientific method can reduce, but not eliminate, uncertainties, and correct mistakes as we go along. Unfortunately, as the autism/vaccine scare shows, unscientific approaches such as the precautionary principle actually feed into the confirmation biases associated with left-wing ideology.

So who is more anti-science, Democrats or Republicans? On the specific issues discussed above, I conclude that the Republicans are more anti-science. However, Berezow is right that scientific "ignorance has reached epidemic proportions inside the Beltway."

Ronald Bailey is reason's science correspondent.