The American polymath and logician Charles S. Peirce (1839–1914) spent much of his professional career working on geodetic measurements. Nevertheless, his very original studies of scientific inference have considerable relevance to geology. Particularly important influences on his views derive from his avid studies of the Scientific Revolution and the Enlightenment, notably the writings of Galileo Galilei (1564–1642) and Immanuel Kant (1724–1804). From Kant, Peirce derived an architectonic and categorical approach to philosophy. Following the example of the Cambridge mineralogist William Whewell (1794–1866), Peirce pursued the history of science in order to uncover the logic of scientific inquiry. His original reading of Galileo revealed that scholar’s reliance upon il lume naturale (“the Light of Nature”) as a guide toward the selection of potentially productive hypotheses from among the many that might be posed in regard to scientific explanation. This principle underpins Peirce’s famous and controversial notion of abduction, or retroduction, i.e., informed guessing, as critical to scientific inquiry. The instinctive tendency of the experienced and informed scientist to “guess right” is essential to the historically demonstrated success of science.