Until now, security had been just one of many campaign themes. A worker at my local supermarket told me he became a Mélenchoniste because the candidate promised a sixth week of annual vacation. He added that he knew Mr. Mélenchon would be “catastrophic” for the French economy, then gave me a guilty look…

Many French voters are already doing that, which means the future of Europe might hinge on pets. An undecided 20-something told me last week that she was waiting to hear the candidates’ views on animals. I assumed she was just an exceptionally committed cat owner, until I saw a poll in which 39 percent of respondents said that animal policy could influence their votes, up from 29 percent in 2012.

How did it come to this, in the birthplace of Voltaire? A special issue of Philosophie Magazine, now on newsstands, explains that anti-Enlightenment thinkers have always popped up here. “They don’t believe in progress,” a headline warns. “They don’t trust democracy. They’re back.”

It helps to have an electorate that’s more schooled in philosophy than economics. The pro-business newspaper L’Opinion warned on Thursday that there’s so much magical thinking on economic matters right now, “we’re not very far from a psychosis.”