Among the greatest inventions of the human mind is doubt.
Doubt of received truth. Doubt of the infallibility of ancestors. Doubt of the shaman, the prophet, the priest. Doubt of majority opinion.
Who was the first person who said "Maybe it's not true what they say"? Who was first, when asked "Why?", replied, "Gee, I don't know"? Who was the first to question the gods?
Among the Greek Epicureans and Skeptics doubt was an indispensable philosophical tool. But somehow that principle was lost in Europe with the rise of institutional Christianity. Dogma reigned paramount. At the time Montaigne was writing his Essays people went to the rack or the stake for the expression of doubt. In Montaigne's France, Catholics and Protestants fought long and barbaric wars over their respective versions of truth.
Somehow Montaigne survived it all. He was a nominal Catholic and theist, but (according to Sarah Bakewell) his essays do not indicate much interest in religion or the afterlife. If he had a religion it was this: Pay attention to everything and doubt all claims to certain knowledge.
But can we live without certainty, or at least some scaffolding of reliable knowledge? Is all-embracing doubt a practical philosophy of life? Can we live comfortably in a shoreless sea of ambiguity? I would guess not.
As it turned out, as Montaigne wrote in his tower, a lad was growing up in Tuscany, Italy, who would marry doubt to reliable knowledge. First, use doubt to clear away received opinion. Then, painstakingly build a new structure of knowledge on the basis of quantitative, reproducible experiment.
If anyone deserves to be called the Father of Modern Science it is Galileo.
Galileo rolled a ball down an inclined plane and observed that the distance traversed went as the square of the time, an experiment that every introductory physics student can repeat today. The rest is history. Out of so simple a beginning came all of the physics, chemistry, biology, geology, and astronomy we enjoy today, not certain knowledge, to be sure, but wonderfully reliable -- a sturdy scaffolding on which to build a skeptical life.
(Internet down this morning.)