Joseph Priestley was an English theologian, chemist, and philosopher, known for his pioneering work in the field of chemistry and for his contributions to the Enlightenment. He is particularly renowned for his discovery of several gases, including oxygen, which he referred to as "dephlogisticated air." Priestley's interest in scientific exploration was closely tied to his theological beliefs and the pursuit of knowledge, which he saw as a way to understand the divine. Throughout his life, Priestley faced significant controversy due to his progressive ideas, especially regarding religion and politics. He was a supporter of the American and French Revolutions, advocating for individual rights and political reform. His views often put him at odds with contemporary society, leading to conflict and ultimately his relocation to the United States, where he continued his research and social advocacy. Despite the challenges he faced, Priestley’s legacy remains significant in both science and philosophy. His work laid the foundation for modern chemistry and his writings contributed to the discourse on democracy and civil rights. Priestley is remembered not just for his scientific discoveries, but also for his commitment to enlightenment ideals that championed reason, progress, and intellectual freedom. Joseph Priestley was an influential English theologian and chemist known for his groundbreaking contributions to chemistry and philosophy during the Enlightenment. He made notable discoveries, including oxygen, which he described as "dephlogisticated air," while intertwining his scientific pursuits with his theological beliefs. Despite facing societal backlash for his progressive ideas, Priestley's work laid essential groundwork for modern science and contributed to discussions on democracy and civil rights, marking him as a critical figure of his time.