An Exhibit at the Chemical Heritage Foundation
Philadelphia, Pennsylvania
23 August 2004 – 29 July 2005


“It may be my fate to be a kind of comet.”

To Thomas Jefferson, his was “one of the few lives precious to mankind.” To John Adams, he was “a comet in the system . . . this great, this learned, this indefatigable, most excellent, and extraordinary man.” He was Joseph Priestley (1733–1804), a mild-mannered stutterer and radical thinker who wrote more than 200 books, pamphlets, and articles that challenged commonly accepted views on science, politics, education, and religion. Joseph Priestley, Radical Thinker, an exhibit at the Chemical Heritage Foundation, combined objects and images from a variety of collections to illuminate the life and work of this singular man on the bicentennial of his death. Some objects originally owned by Priestley were assembled together in the exhibit for the first time in nearly 200 years.

“The doctrine of air . . . now . . . throws the greatest light on the most important processes.”

Priestley’s chemical achievements include the isolation of oxygen and identification of its properties, as well as those of seven other gases, between 1772 and 1775. He demonstrated the carbonation of water and advanced an understanding of the role of blood in respiration and the process of photosynthesis. An innovative experimenter who investigated nature firsthand, Priestley published his methods and experimental results for any educated person to inspect and replicate, thus contributing to a culture of science as a free and open exchange of ideas. To honor his achievements, the American Chemical Society named its most prestigious award the Priestley Medal.

“We are . . . laying gunpowder, grain by grain, under the old building of error and superstition.”

Priestley believed both in the power of human reason and in its capacity to improve man’s estate. He was connected to the great intellects of the Enlightenment era, including John Adams, Thomas Jefferson, Josiah Wedgwood, and Antoine Lavoisier. He believed that government existed only to secure the common good and should not interfere in religion, education, free speech, and economics. In promoting these views, Priestley encouraged the Americans and the French in their attempts to establish republics. In 1791 fears that the revolution in France could spread to Britain led to Priestley’s being branded a dangerous radical by his own government. He and his family were forced to flee a mob that attacked his house and laboratory in Birmingham.

“I can truly say that I considered the office of Christian minister as the most honorable of any upon the earth.”

Raised in a dissenting household, Priestley was ordained a minister in 1762, and his vocation informed all his accomplishments and interests. In public and domestic life he advocated a return to the Christianity of the Gospels, and in science he believed that the rational observation of nature would lead to a closer understanding of God. His sermons and books opposed laws that enforced religious conformity, arguing that human reason, if properly instructed, would naturally turn toward “right religion.” Facing continued opposition for his views, Priestley and his family immigrated to America in 1794. His preaching served as the inspiration for the founding of the first Unitarian Society of Philadelphia in 1796. He spent the last 10 years of his life in Northumberland, Pennsylvania, where visitors to the Joseph Priestley House can still tour the last residence and laboratory of this extraordinary man.