Giordano Bruno was a philospher/theologian and an outspoken critic of many of the religious, philosophical, and scientific beliefs of his time. Although he was not a scientist and had limited understanding of disciplines like astronomy, he was a strong defender of the heliocentric theory of our solar system as presented by Nicholas Copernicus. Passionate and confrontational, Bruno was eventually executed as a heretic.

Bruno was born "Fillipo" Bruno in Nola, near Naples, in 1548 to Biovanni Bruno, a soldier, and Fraulissa Savolino. He took the name of Giordano when he entered the Catholic Dominican order in 1563. He was ordained a priest in 1572. His original views and criticisms of accepted theological doctrines soon garnered him an official accusation of heresy in 1576. He first fled to Rome and then France. At Lyons he completed his work Clavis Magna or "Great Key," which described his art of memory-training. Bruno's expertise in memory-training brought him to the attention of many patrons around the world. In 1583 he went to England where, for a short period, he won the favor of Queen Elizabeth. Living in the house of the French ambassador in London, he completed his book Cena de le Cenert ("The Ash Wednesday Supper"), in which he unreservedly accepted the Copernican heliocentric model of our solar system, in which the Sun is the center of the solar system and not the earth, as was widely believed at the time. He also completed De L'Infinito, Universo e Mondi ("On the Infinite Universe and Worlds"), in which he stated that the universe is infinite, with an infinite number worlds, and that all the worlds are inhabited by intelligent beings.

Bruno invariably outraged both his patrons and the institutions that supported him. His travels took him to Wittenberg, Prague, Helmstedt, and Frankfurt, where he taught, wrote extensively on philosophy and theology, and lived off the largesse of others. In 1591 he accepted an invitation from a patron to live in Venice. However, he was arrested by the Catholic Inquisition and tried as a heretic. He initially recanted and was sent to Rome in 1592, where he was imprisoned for the next several years. When he refused to recant his beliefs permanently, he was burned at the stake in 1600.