I was badly shocked and saddened by the vicious terrorist attack that took place in Paris yesterday. I mourn its victims, those from Charlie Hebdo and the police officers who were murdered. I also mourn the policewoman who lost her life today, whether or not that incident was related to yesterday’s terrorist attack. My thoughts and prayers go out to the victims, their families, and to the French people.

At the same time, I join the growing chorus of sentiment in proclaiming, “Je suis Charlie.” The cause of free expression is both noble and vital. One cannot overstate the importance of free expression.

John Stuart Mill made among the strongest arguments for free speech in his classic work, On Liberty. Those arguments resonate as loudly and clearly today as they did when he first put them to paper nearly 150 years ago. He wrote:

[T]hough the silenced opinion be an error, it may, and very commonly does, contain a portion of truth; and since the general or prevailing opinion on any object is rarely or never the whole truth, it is only by the collision of adverse opinions that the remainder of the truth has any chance of being supplied.

That point goes to the heart of Charlie Hebdo's satirical work. The power of its cartoons, from the perspective laid out by Mill, is not that they were "truth" per se (they weren’t), but that they contained “a portion of truth.”

The cartoons presented contemporary perceptions. Those perceptions were grounded in real events and developments taking place across the Mideast and South Asia. Those events and developments, Mill’s "portion of truth," represent a good starting point for a serious dialogue among Muslims and also an interfaith dialogue between Muslims and non-Muslims.

The pathologies and wanton cruelty exhibited by the extremists in the name of Islam are solely and completely the responsibility of those extremists. Silence, though, can lead to those acts being permitted to define far more than the extremists. That’s the message that was conveyed through the cartoons. No good person—Muslim or non-Muslim alike—can permit such perceptions to become de facto reality without risking grave harm to humanity, injury that would far surpass what the terrorists inflict today. As Edmund Burke so succinctly put it, “The only thing necessary for the triumph of evil is for good men to do nothing.”

Therefore, yesterday’s brutal attack must serve as a clarion call for a renewed and robust defense of free speech. Free expression, not all of which is tasteful and some of which can shock the senses, is the lifeblood of creativity, innovation, research and inquiry, learning, and human progress.

Neither France nor the West can afford to compromise when it comes to safeguarding this most basic freedom. The costs of doing so would vastly outweigh any perceived or actual benefits. Without free expression, France cannot be France and the West cannot be the West. Therefore, like so many here, I stand in full solidarity with my friends in France at their time of peril and enormous sadness, and with good people all across the world, in declaring, “Nous sommes tous des Charlie.”