In the years before the Civil War, slaveholders were the greatest threat to free speech in the United States. White Southerners used state laws, a congressional gag rule, suppression of the mail, and physical violence to silence abolitionist speech because they believed it was dangerous.

In 1830, for example, Louisiana penalized anyone using “language in any public discourse, from the bar, the bench, the stage, the pulpit, or in any place whatsoever,” as well as “in private discourses or conversations,” that had “a tendency to produce discontent among the free colored population of this State, or to incite insubordination among the slaves therein.” In other words, those who spoke out against slavery or racial discrimination would be in violation of this law. The mandated punishment ranged from three to 21 years of hard labor to death.

If Democrats refused to permit antislavery Americans to voice their opinions, there would be nowhere to turn but to violence.

Other states enacted identical statutes. As one South Carolina newspaper declared, the topic of slavery “shall not be open to discussion.”

Speaking out against slavery in the United States took courage. If anti-speech laws were not enough, mobs filled in the gaps. Some abolitionists were brutally beaten while others were murdered.

Abraham Lincoln engaged this issue in a speech he delivered at the Cooper Union in New York City in February 1860. Speaking directly to white Southerners, he said, “You consider yourselves a reasonable and a just people. Still, when you speak of us Republicans, you do so only to denounce us a reptiles, or, at the best, as no better than outlaws.” Lincoln pointed out that Southern Democrats were more likely to “grant a hearing to pirates or murderers” than to Republicans.

Indeed, when white Southerners gathered, Lincoln said that “an unconditional condemnation” of Republicans was “the first thing to be attended to.” In fact, it was “an indispensable prerequisite — license, so to speak — among you to be admitted or permitted to speak at all.”

Lincoln then asked, “Now, can you, or not, be prevailed upon to pause and to consider whether this is quite just to us, or even to yourselves?”

In asking this question, Lincoln was encouraging his Democratic opponents to reflect on the consequences of restricting free speech. Only through the free exchange of opinions could the best ideas gain sway. As Oliver Wendell Holmes Jr. would argue many decades later, “The ultimate good desired is better reached by free trade in ideas.” He continued: “The best test of truth is the power of the thought to get itself accepted in the competition of the market.”

When slaveholding Democrats and their Northern allies tried to silence words and ideas they disagreed with simply because they believed them false or dangerous, they were denying both their political opponents and themselves the opportunity to reach new and better conclusions.

Slaveholders believed that open debate about slavery caused servile insurrections. If they could silence the Republican Party, they reasoned, they could eliminate the danger.

But Lincoln disagreed. “There is a judgment and a feeling against slavery in this nation, which cast at least a million and a half of votes,” he said. “You cannot destroy that judgment and feeling — that sentiment — by breaking up the political organization which rallies around it.” But if they could, he asked, “How much would you gain by forcing the sentiment which created it out of the peaceful channel of the ballot-box, into some other channel? What would that other channel probably be? Would the number of John Browns be lessened or enlarged by the operation?”

This was a stark warning to white Southerners. They might believe that they would win the day by silencing their political opponents. But stifling speech would not eliminate the widespread belief that slavery was evil. And if Democrats refused to permit antislavery Americans to voice their opinions, there would be nowhere to turn but to violence.

In his stirring peroration, Lincoln spoke directly to Republicans, urging them to hold firm in their convictions even if they were maligned or worse. “Neither let us be slandered from our duty by false accusations against us, nor frightened from it by menaces of destruction to the Government nor of dungeons to ourselves,” he said. “Let us have faith that right makes might, and in that faith, let us, to the end, dare to do our duty as we understand it.”

In this closing line, Lincoln inverted the typical aphorism “might makes right.” He wanted his fellow Republicans to believe that their ideas were persuasive, and that they could carry a presidential election if they would only stand up and make the case for their positions. Well-reasoned arguments, in short, could create political majorities that would pursue justice.

Abraham Lincoln offers lessons that are as true today as they were in 1860. If democracy in the United States is to flourish, we must foster habits of mind among our citizens that promote the free exchange of ideas.

Editor’s note: This article was originally published by RealClearHistory and made available via RealClearWire.