Joseph Priestley
Unitarian Universalists know Joseph Priestley as a famous Christian Unitarian minister who brought Unitarianism to our country. Scientists know Joseph Priestley as a famous chemist, credited with the discovery of oxygen. His science was integral to his theology, fusing Enlightenment rationalism with Christian theism. His major argument was that the only revealed religious truths that can be accepted are those that match one's experience of the natural world.
Joseph Priestley was born in 1733 in England to a Calvinist family that dissented from the official Church of England, and was raised by his father's sister, who was tolerant of diverse theological views. He was sent to alternative schools founded by religious dissenters that taught more diverse subjects than state-supported schools, subjects that included the sciences. While still a student, he was able to refute the Trinitarian view of God and wrote his most influential theological work, Institutes of Natural and Revealed Religion. After beginning his career, he took up appointments as a minister in several small towns and taught classes in a number of schools. At the height of his career, he was called to be the minister of a large chapel in Leeds England. A decade later, however, his career began to unravel. His religious works, like the History of the Corruptions of Christianity, his opposition to establishment of Christianity as a state religion, and his enthusiasm for the French revolution, led to riots by an angry mob that burned his church, home, and laboratory. At the end of his career, he had to avoid prison by leaving England for America.
When he came to the newly formed country of the United States and briefly settled in Philadelphia, he was disappointed to learn that he could not find a Christian church that would let him preach from their pulpit. Eventually, with contributions from religious sympathizers and help from Universalists, he delivered a series of sermons at a new Universalist church in 1796 that led to the founding of the very first Unitarian church in America.
He worked during a era when chemists were learning that the myriad compounds found in nature were made from simpler elements, and that elements could be taken apart and combined again to make new compounds. His work with what he called "fixed air" and soda water led to an understanding of carbon dioxide, and his discovery that plants can restore air that animals respired was a piece of the understanding of photosynthesis. His most elegant experiments involved production of a gas from mercuric oxide that caused candle flames to burn more brightly, a gas that he called "dephlogisticated air", which we now know as oxygen.
Joseph Priestley was a radical in his time, surrounded by controversy wherever he went. And one of the more radical ideas was that for him, science and religion were simply two different ways of seeking truth in the world around him, one seeking the truth about matter and the other seeking the truth about spirit.