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Three centuries ago, in a land 3,000 miles away, a revolution in reason began known as The Age of Enlightenment. Apropos our gathering here today, it is also called the Age of Reason, or in the descriptor of great German philosopher Immanuel Kant—Sapere Aude!—dare to know! “Have the courage to use your own understanding!” As Kant wrote: “Enlightenment is man’s emergence from his self-imposed immaturity. Immaturity is the inability to use one’s understanding without guidance from another.”

The Age of Reason, then, was the age when humanity was born again, not from original sin, but from original ignorance and dependence on authority. Never again shall we allow ourselves to be the intellectual slaves of those who would bind our minds with the chains of dogma and authority. In its stead we use reason and science as the arbiters of truth and knowledge.

This great Age of Reason came about because of a prior movement called The Scientific Revolution, when people began to look and think for themselves. Before science, truth about the world was the product of superstition and magical thinking, intuition and emotion, subjective feelings confirmed by selective perception. With science there is a method to get at the truth, an experimental method of checking with the world to see if your beliefs are true or not. Here are just a few of the benefits that reason has given us…

Instead of divining nature through the authority of an ancient book, through travel and exploration people examined the book of nature for themselves.

Instead of looking at illustrations in illuminated botanical books scholars went out into nature to see what was actually growing out of the ground.

Instead of relying on the woodcuts of dissected bodies in old medical texts, physicians opened bodies to see with their own eyes what was there.

Instead of burning witches after considering the spectral evidence as outlined in the Malleus Maleficarum—the authoritative book of witch hunting—jurists began to consider other forms of more reliable evidence.

Instead of human sacrifices to assuage the angry weather gods, naturalists made measurements of temperature, barometric pressure, and winds to create a science of climate.

Instead of enslaving people because they were a lesser species, we expanded our biological knowledge to include all humans as members of the species.

Instead of treating women as inferiors because a certain book says it is man’s right to do so, we discovered natural rights that dictate all people should be treated equally.

Instead of labeling homosexuality an abomination, or atheists and nonbelievers as immoral non-citizens, we are today engaged in a great legal struggle to make this final legal hurdle in the long rights revolution.

Instead of the supernatural belief in the divine right of kings, people employed a natural belief in the legal right of democracy, and this idea too is now spreading around the globe.

Democratic elections, in this sense, are like scientific experiments: every couple of years you carefully alter the variables with an election and observe the results.

Liberal democracy works better than any other form of government tested because democracy, like science, is a method, not an ideology. As the intellectual giant whose monument stands nearby as a tribute to all that is good and right about reason—Thomas Jefferson—wrote in 1804:

No experiment can be more interesting than that we are now trying, and which we trust will end in establishing the fact, that man may be governed by reason and truth.

But as Jefferson also warned, “Eternal vigilance is the price of liberty.”

And so as we rally here today to celebrate reason, let us also remember that we must never let down our guard, for there are those still who would prefer to live in a Medieval world of superstition and dogma. There is no guarantee that reason will triumph over ignorance.

Still, let us celebrate what we have accomplished over the centuries and note the progress so well captured in the memorable observation by that other great freedom fighter, Martin Luther King, Jr., who proclaimed: “Let us realize the arc of the moral universe is long but it bends toward justice.”

The force behind this moral arc is reason and science. To that end let us “Thank Reason” for our blessings of liberty.

Thank Reason for our democracy.

Thank Reason for our rights.

Thank Reason for our prosperity.

And Thank Reason for our freedom.