On Dec. 14, the Trump administration provided policy analysts at the Centers for Disease Control and Prevention (CDC) with a list of forbidden words and phrases. Analysts were told that when they sought funding for various projects, it would be best to avoid them. Two of the prohibited phrases were "science-based" and "evidence-based." The response from scientists, public health officials, the media, and the public was swift and one-sided. How was the CDC, a science- and evidence-based organization, supposed to avoid these phrases? And, more importantly, why should they?

In truth, the forbidden words directive shouldn't have been so surprising. Science denialism isn't new to the Trump administration.

During the run-up to the election, candidate Trump declared that vaccines caused autism, ignoring 26 studies that showed they didn't. He even met with prominent anti-vaccine activists, hinting, at least according to one, at a place in his administration.

Once in office, President Trump appointed Scott Pruitt to head the Environmental Protection Agency and Rick Perry to head the Department of Energy. Both Pruitt and Perry share President Trump's view that the 7 billion humans on the planet haven't affected the environment; all willing to ignore the fact that increasing levels of carbon dioxide caused by human activity have altered our climate.

Trump's pick for Vice President, Mike Pence, and for Secretary of Education, Betsy DeVos, are evolution denialists; both willing to ignore the roughly 250,000 years of fossil records showing that man and ape evolved from a common ancestor. Instead, they choose to believe that humans were created on a single day.

In some instances, the Trump administration offered policy analysts at the CDC alternative phrases. Instead of "science-based" or "evidence-based" the CDC could say that it "bases its recommendations on science in consideration with community standards and wishes." In other words, science is just another voice in the room, on equal footing with all other voices, no matter how ill informed or unsubstantiated those other voices might be.

Science isn't particularly democratic. It can't be harnessed by ill-founded community beliefs or tailored to fit the Zeitgeist. Scientists formulate a hypothesis, establish burdens of proof, and subject those proofs to statistical analysis. Eventually certain truths emerge. And while people can reasonably hold contrary views about religion or philosophy or politics, science doesn't work that way. Gravity, evolution, climate change, and the safety of vaccines aren't matters of debate; they're facts built on a mountain of evidence.

In Feb. 2017, Kyrie Irving, a point guard for the Boston Celtics, told the Washington Post that he believed that the earth was flat. Irving isn't alone. The Flat Earth Society boasts more than 500 members on its website, all of whom are willing to ignore photographs of the earth from space showing that it's round. If scientists are now supposed to yield to "community wishes," shouldn't we at least consider policies based on the beliefs of the Flat Earth Society? Wouldn't it be reasonable to ask Kyrie Irving to head NASA?

The Flat Earth Society analogy takes the Trump administration directive to its illogical end. But by denying the science of climate change and putting our children's futures at risk, it is fairly safe to conclude that science denialism has already reached its illogical end.

Paul A. Offit, MD, is a professor of pediatrics at the Perelman School of Medicine at the University of Pennsylvania and a member of CDC working groups. He is also the author of the forthcoming book 'Bad Advice: Or Why Celebrities, Politicians, and Activists Aren't Your Best Source of Health Information.'