The next time you take a deep breath, think for a moment of Joseph Priestley, the 18th-century British scientist widely credited with discovering oxygen.
As Steven Johnson explains in his engaging study of Priestley, The Invention of Air: A Story of Science, Faith, Revolution, and the Birth of America, the circumstances surrounding Priestley's signature achievement are "far more vexed than the standard short-form biographies suggest." That's because "discovering 'oxygen' is not like 'discovering' the Dead Sea Scrolls….It is closer to, say, discovering America: the meaning of the phrase depends entirely on the perspective and values you bring to the issue."
Along with his contemporaries Antoine Lavoisier and Carl Wilhem Scheele, Priestly isolated oxygen gas and was the first to draw connections between "pure air" and blood. However, as Johnson notes, Priestley was trapped within a rapidly failing scientific paradigm, phlogiston theory, which limited his ability to fully understand and accept what he was witnessing in his own experiments. One of the great dead ends in scientific discourse, phlogiston theory was a fanciful and massively influential attempt created in the 16th and 17th centuries to explain combustion, rust, and other forms of oxidation by replacing the ancient Greek elements (fire, water, air, and earth) with a series of previously undiscovered substances. Ironically, Lavoisier would ultimately use Priestley's own experiments as the basis for refuting phlogiston theory and creating what we now know as chemistry. Like a laboratory Moses, Priestly pointed the way for others to a destination at which he could not quite arrive.
By the time he died in America in 1804, Priestly had managed to isolate and name 10 gases, become known as "the father of modern chemistry," and, perhaps most wonderfully, invented soda water. He had emigrated to Pennsylvania in 1794, after inspiring an English mob to burn down his laboratory due to his radical Unitarian views, which blended respect for Jesus' moral teachings and an insistence on his lack of divinity. (That may be Priestley's most amazing achievement: Stoking people to violence through Unitarianism!) He was a major influence on his friend Benjamin Franklin and other leading scientists of the day, and his political and pedagogical work left a huge impression on Founding Fathers such as Thomas Jefferson.
Johnson paints Priestley not as a man of the past but precisely the sort of figure the world needs more than ever: A searcher who shared his discoveries openly and willingly, crossed disciplinary boundaries with impunity and insight, who conceived of the world as a large laboratory. As important, Priestley exemplifies "the temperament that we expect to find at the birth of America— bountiful optimism, an untroubled sense that the world must inevitably see the light of reason."
We live in troubling times, filled with signs of a great economic apocalypse, politicized science on topics from birth control to climate change, and religious zealots who kill innocents rather than live peacefully with them. This is exactly the moment to learn from Priestley, who survived riots, threats of prosecution, and other hardships and yet never doubted that "the world was headed naturally toward an increase in liberty and understanding." Ironically, The Invention of Air underscores that there is nothing natural about progress and liberty, each of which must be fought for and defended every single day by visionary individuals.