Voltaire learned early in his writing career about the danger of censorship at the hands of the powerful. When a minor argument with the Chevalier of Rohan resulted in his unlawful imprisonment in the Bastille, he was forced into exile to retain freedom of speech. It was a bargain that has immeasurably benefited the world.
While in exile, he wasted no time offending the French "royal censor" (yes, that was a thing) by publishing Lettres philosophiques, which was subsequently banned and burned for criticizing the French monarchy.
Voltaire was the father of the Enlightenment, and his name is synonymous with the age. As Hugo said, "To name Voltaire is to characterize the entire eighteenth century." He was the leading progenitor of the principles that have become our modern liberal values - most notably that universal freedom of speech is far better for the world than tightly controlled, centralized sense-making by the "established authorities," whomever they might be and whatever their claim to truth.
In our illustration, we give this quotation a modern, Orwellian twist. A simple equation is given a "truth" makeover by the authorities. We'd like to think that Voltaire's objection to the depicted defacing would not so much be the false assertion of the five, but the censorship of the four. Voltaire would have equally defended the five had it been the other way around, and therein lies the genius of his principle. As he is often paraphrased as saying, "I do not agree with what you say, but I will defend to the death your right to say it."