Donald Trump is often simply wrong about science, denying climate change and furthering the myth that vaccines cause autism. PHOTOGRAPH BY JOE RAEDLE / GETTY

Over the past few months, we’ve seen Donald Trump lower, again and again, the bar for political discourse. All the while, though, he’s been lowering the scientific bar, too. In May, for instance, while speaking to an audience of West Virginia coal miners, Trump complained that regulations designed to protect the ozone layer had compromised the quality of his hair spray. Those regulations, he continued, were misguided, because hair spray is used mainly indoors, and so can have no effect on the atmosphere outside. No wonder Hillary Clinton felt the need to include, in her nomination speech, the phrase “I believe in science.”

Often, Trump is simply wrong about science, even though he should know better. Just as he was a persistent “birther” even after the evidence convincingly showed that President Obama was born in the United States, Trump now continues to propagate the notion that vaccines cause autism in spite of convincing and widely cited evidence to the contrary. (As he put it during a Republican debate, last September, “We’ve had so many instances. . . . A child went to have the vaccine, got very, very sick, and now is autistic.”) In other cases, Trump treats scientific facts the way he treats other facts—he ignores or distorts them whenever it’s convenient. He has denied that climate change is real, calling it pseudoscience and advancing a conspiracy theory that “the concept of global warming was created by and for the Chinese in order to make U.S. manufacturing noncompetitive.” But he has also filed a permit request to build a sea wall around one of his golf courses, in Ireland, in order to protect the property from global warming and its consequences. Which Trump is running for President?

Mike Pence, Trump’s running mate, has a more consistent record on science; unfortunately, it’s consistently bad. Pence is an evangelical Christian who is adamantly opposed to embryonic-stem-cell research; in a conversation with Chris Matthews, in 2009, Pence hedged on whether he believes in evolution. Even when it comes to more secular matters, Pence has made some outrageous claims. In 2001, he published an essay piece on his campaign Web site claiming that smoking doesn’t kill. As if to support that claim, he noted in the same piece that one out of three smokers dies from smoking-related illnesses. Pence seems to think that thirty-three per cent and zero per cent are the same.

As if all this weren’t enough, Trump has argued for downsizing the Department of Education and said that the U.S. invests too much money in K-12 schooling. He has suggested that he might appoint Ben Carson—a young-Earth, anti-evolution creationist—to advise him on educational reform. He has called the National Institutes of Health “terrible,” and has said that he would eliminate the E.P.A. In April, the science journal Nature reported that his anti-immigrant tirades could be hindering efforts to recruit good scientists and students to the U.S. The list goes on.

The differences between the candidates and their parties could not be more stark. Hillary Clinton has a long history of supporting scientific research; she has long understood the connections between that research and economic development. She has said that, if elected, she would increase funding for the National Science Foundation and the National Institutes of Health. As a senator, in 2001 and 2002, she co-sponsored legislation that would have expanded support for stem-cell research. While she hasn’t gone as far as Bernie Sanders in arguing for a carbon tax, Clinton has spoken out strongly about the need to address climate change. Recently, she announced that she would seek to install half a billion solar panels by 2020, and to shift a third of America’s electricity production to renewable resources by 2027. Clinton has also endorsed proposals to enhance STEM in schools, including new-teacher training. Partly as a response to Sanders’s candidacy, she has even pledged to make public colleges and universities tuition-free for families making an annual salary of less than eighty-five thousand dollars today, and less than a hundred and twenty-five thousand dollars by 2021.

On the level of party platforms, too, the differences are extreme. Perhaps in response to Trump’s candidacy, the 2016 Republican Party platform extends policy proposals that were, in 2012, already anti-science. The platform proposes eliminating the current Administration’s Clean Power Plan; prohibiting the E.P.A. from regulating carbon dioxide; officially declaring that climate change is “far from this nation’s most pressing national security issue”; and dissenting from international agreements such as the Kyoto Protocol and the Paris Agreement. The platform also claims that it is illegal to contribute to the U.N.’s Framework Convention for Climate Change and its Green Climate Fund because of the Palestinian Authority’s membership in the United Nations. It opposes embryonic-stem-cell research and human cloning for research purposes.

The positions taken by Trump and the Republicans have consequences beyond science itself. Essentially, they are betting that, for a significant portion of the country, empirical reality doesn’t matter; they are also signalling that empirical reasoning won’t be the basis of their public policy. Today, of course, we face global challenges such as climate change, which are more urgent than any we have ever confronted. These challenges require a sober assessment of reality. When science is distorted on the campaign trail, it may produce applause lines. But if those distortions lead to bad public policy, the quality of people’s lives will suffer.