When French noblemen were sentenced to die under the ancien regime, their heads were chop-ped off on the block. However, commoners were sent to the wheel or the gallows and, sometimes, they were quartered. Dr Joseph Guillotin was offended by such social injustice, and he resolved to end it.
A respected physician and member of the French parliament during the first years of the revolution, he promoted equal rights for the condemned and called for a machine that offered the same "sweet" death to aristocrats and journeymen alike. On 10 October 1789, he outlined the device he had in mind and said that its victims would feel nothing more than "a light breeze on the back of the neck".
The guillotine or "Guillotin's child", as it was sometimes called, cut off 40,000 heads during the Great Terror in the 1790s, and continued to function until capital punishment was abolished in France by President Francois Mitterrand almost 200 years later. But does its inventor deserve his grisly place in history?
A new biography, Le docteur Guillotin, by the French historian Henri Pigaillem, suggests not. Far from being a bloodthirsty zealot, argues Pigaillem, Guillotin was a decent man - a philanthropist who dedicated his life to worthy causes, "a benefactor of humanity".
By 1803, he was leading another campaign, this time for the introduction of vaccinations against smallpox. Pigaillem recounts how he was opposed by the French medical establishment, but won over the doubters when he produced figures proving the benefits of a vaccination. Millions of lives were saved as a result.
This was by no means Guillotin's only achievement. He worked hard to improve health services and denounced the hygiene of Parisian hospitals in a report that prompted the ancien regime - in one of its final acts - to build four new hospitals. He successfully called for France's first medical academy. He became a member of an avant-garde association, la Societe des Amis des Noirs (the Society of Friends of Black People), which wanted an end to slavery. And he drew up a petition, signed by thousands, which called for the commons to have as many seats as the nobility and the clergy in the States General, the assembly summoned by Louis XVI on the eve of the revolution.
But Guillotin was not a natural politician. Reserved and retiring, he was a poor speaker and preferred back-room committees to public grandstanding. In two years as a parliamentarian, he made only two noteworthy utterances.
The first concerned the smell at the States General. "The heavy and pestilential air exhaled from the bodies of 3,000 people concentrated in this room will inevitably produce a dire effect on the members present," he said. "I think the assembly must order openings wide enough for the air to circulate." The second focused on capital punishment. Pigaillem says inequality in death was a nagging concern to Guillotin, although not the issue that worried him most. He was more interested in fighting insalubrity in hospitals.
But when he stood up to make his speech about the death penalty, the words flowed with unusual passion and eloquence. "The mechanism falls like lightning, the heads flies off, the blood spurts out, the man exists no more."
From then on, whenever newspapers mentioned the Widow, as the guillotine was nicknamed, they mentioned him - though he had little input into the design, which was based on similar, if less sophisticated, instruments that were already in use elsewhere in Europe. When tests were carried out successfully in France, first on sheep, then on dead bodies, the triumph was his. When the first condemned man was guillotined in April 1792, the good doctor was given the credit.
By then, Guillotin had his own doubts - not about the instrument itself, but about the people into whose hands it had fallen. "He has Hell in his face, in his character and in his future," he said of Robespierre.
A decade later, Guillotin's doubts had been confirmed. "He is inconsolable," said Josephine, Napoleon's wife. "His venerable face carries the mark of a profound sadness. If death had been less swift, perhaps the people would have grown tired of these executions sooner."