“He who can go to the fountain
does not go to the water-jar.”
—Leonardo da Vinci
I have more respect for Leonardo than for any other curious human I’ve ever heard of. He may have been the most restless investigator of all. Kenneth Clark called him “the most relentlessly curious man in history.” He was also weird, surpassingly weird, in his interests, which were as wide and unexpected as the limits of imagination.
His notebooks were filled with observations, math equations, drawings of sawed-open skulls, of severed arteries, of water eddies, of explosions and flying machines, full also of to-do lists that chronicle his boundless curiosity. Walter Isaacson collected some samples from one day’s entry:
“Measure Milan and its suburbs.
Get the master of arithmetic to show you
how to square a triangle.
Ask Giannino the Bombardier
about how the tower of Ferrara is walled.
Describe the tongue of a woodpecker.
Ask Benedetto Protinari by what means
they walk on ice in Flanders.
Get a master of hydraulics to tell you how to
repair a lock, canal and mill in the Lombard manner.
Go every Saturday to the hot bath where
you will see naked men.
Observe the goose’s foot; if it were always open
or always closed the creature would not be able
to make any kind of movement.
Draw Milan.
Get the measurement of the sun promised me by
Maestro Giovanni Francese, the Frenchman.”
What I hope you’ll notice and find inspiring is that Leonardo took nothing for granted, cultivated sources that would provide him the information he sought, and prized most of all his own observations or the direct testimony of other keen observers.

He went to the fountain,
not to the water-jar.
When Google leads you to a magazine article that says, “The study concluded that the earth is not actually getting warmer,” you’re drinking from the water-jar. You can either trust Coalminer Times, or you can be like Leonardo. Follow the lead back to the fountain. Find the study that did the testing and tracked the temperatures and drew the conclusions. See for yourself what conclusions they drew.
Are they the same conclusions Coalminer Times reported them to be? Who conducted the study? Who financed it? Was it someone interested in tracking the earth’s temperature? Or was it someone interested in promoting coal?
If the study turns out to be a collection of other people’s opinions, you’ve found the tank from which the jars were filled. Keep looking. The world is full of water tanks and water jars tainted with water from suspect sources. And very few fountains.
References
Isaacson, W. (2018). Leonardo Da Vinci. New York: Simon & Schuster Paperbacks.