Galileo (1564–1642) rejected the teleological view of nature espoused by Aristotle and embraced by Thomas Aquinas in his fifth argument for God's existence. Galileo didn't think it was the Bible's place to instruct about the astronomical data describing the workings of the universe. Thus his famous remark, the Bible is “to teach us how to go to heaven, not how the heavens go.” An empiricist astronomer, philosopher, and mathematician, Galileo thought that the way to understand “the book of nature” is to read it in the language of mathematics.

Galileo was born on February 15, 1564, in Pisa. He and his family moved to Florence in 1572. He nearly became a priest, but after a short period of study he left and enrolled at the University of Pisa to earn a medical degree. He didn't finish that degree either, but instead studied mathematics notably. In 1592 he was appointed, at a much higher salary, to the position of mathematician at the University of Padua.

It was during his Paduan period that Galileo worked out much of his mechanics and began his work with the telescope, which had been invented by the Dutchman Hans Lippershey in 1608. In 1610 Galileo published The Starry Messenger, and soon after accepted a position as mathematician and philosopher to the Grand Duke of Tuscany (and a nonteaching professorship at Pisa). Late in 1610, the Collegio Romano in Rome certified the results of Galileo's telescopic observations as presented in his book. In 1611 he became a member of the first scientific society, the Academia dei Lincei.

In 1613–14 Galileo entered into discussions of Copernicanism through his student Benedetto Castelli, and wrote a Letter to Castelli on the Reltionship Between Science and the Bible. In February 1616, the Sacred Congregation of the Index condemned Copernicus's book On the Revolution of the Heavenly Orbs, pending correction. Galileo then was called to an audience with Cardinal Robert Bellarmine and advised not to teach or defend Copernican theory.

In 1623 Galileo published The Assayer, in which he dealt with the nature of comets, arguing that they were sublunary phenomena. In this book, he made some of his most famous methodological pronouncements, including the claim that the book of nature is written in the language of mathematics. The same year Maffeo Barberini, Galileo's supporter and friend, was elected Pope Urban VIII. Galileo felt empowered to begin work on his Dialogues Concerning the Two Great World Systems. It was published with an authoriztion from Florence (and not Rome) in 1632. Shortly afterward the Inquisition banned its sale, and Galileo was ordered to Rome for trial. In 1633 he was condemned. In 1634, while Galileo was under house arrest, his daughter, Maria Celeste, died. At this time he began work on his final book, Discourses and Mathematical Demonstrations Concerning Two New Sciences. This book was smuggled out of Italy and published in Holland. Galileo died early in 1642. Due to his conviction, he was buried obscurely until 1737.