The Slave Who Transformed Cotton Mather From Witch Hunter Into Science Innovator

This week, after 150 years, Jack Daniels finally came clean that its famed whisky recipe came courtesy of a Tennessee slave. This is, of course, by no means the only example of a slave’s contribution to American industry and culture being, at worst, stolen and, at best, minimized or completely forgotten. There was Baltimore slave Benjamin Bradley’s steam engine. And a Mississippi slave known only as Ned’s cotton scraper. And then, there was Boston’s own Onesimus.

While Massachusetts was among the first states to abolish slavery, it was also one of the first to embrace it. In 1720’s Boston, buying a human being was apparently an appropriate way to thank your local man of God.

"He was presented to Cotton Mather by his congregation as a gift, which is, of course, extremely troubling," said Brown University history professor Ted Widmer.

Cotton Mather was a true puritan. A towering — if controversial — figure, especially following the Salem witch hysteria to which his preaching and writings greatly contributed.

"Mather was interested in his slave whom he called Onesimus, which was the name of a slave belonging to St. Paul in the Bible," Widmer explained .

Described by Mather as a “pretty intelligent fellow,” Onesimus had a small scar on his arm, which he explained to Mather was why he had no fear of the era’s single deadliest disease: smallpox.

"Mather was fascinated by what Onesimus knew of inoculation practices back in Africa where he was from," Widmer said.

Viewed mainly with suspicion by the few Europeans of the era who were even aware of inoculation, it’s benefits were known at the time in places in places like China, Turkey and Onesimus’ native West Africa.

"Our way of thinking of the world is often not accurate," said Widmer. "For centuries Europe was behind other parts of the world in its medical practices."

Bostonians like Mather were no strangers to smallpox. Outbreaks in 1690 and 1702 had devastated the colonial city. And Widmer says Mather took a keen interest in Onesimus’ understanding of how the inoculation was done.

"They would take a small amount of a similar disease, sometimes cowpox, and they would open a cut and put a little drop of the disease into the bloodstream," explained Widmer. "And they knew that that was a way of developing resistance to it."

When a smallpox outbreak once again gripped Boston in 1721, Mather enlisted Zabdiel Boylston, one of the few physicians of the time willing to gamble on Onesimus’ procedure. Mather, who once railed against a “horrible plot against the country by witchcraft,” was now advocating for cutting-edge science.

"He was vilified," said Widmer. "A local newspaper, called the New England Courant, ridiculed him. An explosive device was thrown through his windows with an angry note."

That Bostonians knew exactly where Mather and Boylston’s inoculation ideas came from only added to the outcry.

"There was an ugly racial element to the anger," said Widmer. "That it had come from Africa made it even scarier. It did seem like a kind of black. and one local Bostonian blamed him for what he called Cotton Mather’s negro-ish thinking."

Nevertheless, on June 26, 1921, Boylston began employing Onesimus’ technique at Mather’s urging, inoculating two of his slaves, and his own son.

"It was much better science than what they had at their disposal, which was old fashioned folk remedies or a lot of prayer which did nothing against small pox," said Widmer.

Bostonians of the era were fastidious record keepers, and while only 248 chose to be inoculated, the numbers revealed its stunning effectiveness in what looks – to our modern eyes – very much like the city’s first clinical trial. 

"A few people who got inoculated did die. But roughly one in 40 did, and roughly one in seven members of the general population dies, so you had a much worse chance of surviving small pox if you did nothing."

Mather and Boylston both wrote about their findings, which were circulated at home and impressed the scientific elite in London, adding invaluable data at a crucial time that helped lay the groundwork for Edward Jenner’s famed first smallpox vaccine 75 years later.

"Even though most of the city was on the wrong side and didn’t want inoculation to happen they were smart enough to realize afterward that they had been wrong," said Widmer. "And so there was a higher level of respect for science going forward."

The scourge of slavery would continue in Massachusetts for another 60 years, but as for the man whose knowledge sparked the breakthrough...

"Onesimus was recognized as the savior of a lot of Bostonians and was admired and then was emancipated," said Widmer. "Onesimus was a hero. He gave of his knowledge freely and was himself freed."

Boston’s first inoculations, one of the Bay State’s earliest medical breakthroughs, brought about when Cotton Mather put his faith in Onesimus – an enslaved man – 295 years ago this week. 

Editor’s Note: The audio file of this story has been removed because it contained a musical clip that might offend some listeners.

If you have a tale of hidden Massachusetts history—or there is something that you’re just plain curious about—let us know. Email  curiositydesk@wgbh.org. We might just look into it for you.