Victor Davis Hanson examines for National Review Online readers the Left’s inconsistent reliance on sound scientific data as it pushes a political agenda.

President Obama entered office promising to restore the sanctity of science. Instead, a fresh war against science, statistics, and reason is being waged on behalf of politically correct politics.

After the Sandy Hook tragedy, the president attempted to convert national outrage into new gun-control legislation. Specifically, he focused on curtailing semi-automatic “assault” rifles. But there is no statistical evidence that such guns — semi-automatic rifles that have mostly cosmetic changes to appear similar to banned military-style fully automatic assault weapons — lead to increased gun-related crimes. …

… The president still talks of “settled science” in the global-warming debate. He recently flew to California to attribute the near-record drought there to human-induced global warming.

There is no scientific basis for the president’s assertion about the drought. Periodic droughts are characteristic of California’s climate, both in the distant past and over a century and a half of modern record-keeping. If the president were empirical rather than political, he would instead have cited the logical reasons for the fact that this drought is far more serious than those of the late 1970s. …

… The administration has delayed construction of the proposed Keystone XL pipeline, citing concern about climate change. Yet a recent State Department environmental report found that the proposed pipeline would not increase carbon dioxide emissions enough to affect atmospheric temperatures. There is no scientific basis from which to cancel the Keystone, but a variety of logical reasons to build it — such as moving toward North American energy independence and protecting ourselves against energy blackmailers and cartels abroad.

Science is rarely “settled.” Instead, orthodoxy is constantly challenged. A theory survives not by politics, but only if it can offer the best logical explanations for a set of circumstances backed by hard statistical data.