To those encountering him for the first time, Voltaire can look like a historical curiosity. His archaic wig and libertine wit seem to belong to a forgotten corner of the past. Moreover, he can be considered a conservative. He curried favor with the high and mighty, especially Louis XV. He was so deeply committed to the cultural system developed under France’s previous ruler, Louis XIV, that he would fail any test of political correctness today. And Voltaire opposed education for the masses because, he said, someone had to tend the fields.

So, forget the wig. But reconsider the wit. Nothing works better than ridicule in cutting bigots down to size. “I have never made but one prayer to God,” Voltaire wrote, “a very short one: ‘O Lord, make my enemies ridiculous.’ And God granted it.” The first of the two most powerful weapons in his arsenal was laughter: “We must get the laughter on our side,” he instructed his auxiliary troops in the salons of Paris.

Ridicule works outside salons. We in America have Stephen Colbert on television. We had H.L. Mencken in the newspapers and Mark Twain in books. Yet wit can sound elitist, and Voltaire cultivated the elite, especially in his youth, when he celebrated wealth, pleasure and the good things of life. His poem “Le Mondain,” written in 1736, is an apology for worldly luxury — “the superfluous, a very necessary thing,” he wrote, in opposition to Christian asceticism.

That was Voltaire the young libertine. But now, in our contemporary crisis, I propose that we look also to Voltaire the angry old man. It was in his old age, during the 1760s and 1770s, that he wielded his second and most powerful weapon, moral passion.

In 1762 Voltaire learned about a case of judicial murder. The Parlement (high court) of Toulouse had condemned a Protestant merchant, Jean Calas, to be tortured and executed for supposedly killing his son, who supposedly had intended to convert to Catholicism. Not only were the suppositions wrong, but strong evidence pointed to Calas’s innocence.