Lecture on the High Medieval Church by Professor Lisa M. Lane, MiraCosta College. CC 2008. (Creative Commons Attribution-Noncommercial-ShareAlike licensed.)
6. Faith and Reason It must be said that God's existence can be proved in five ways. The first and most obvious way is based on the existence of motion. It is certain and in fact evident to our senses that some things in the world are moved. Everything that is moved, however, is moved by something else, for a thing cannot be moved unless that movement is potentially within it. A thing moves something else insofar as it actually exists, for to move something is simply to actualize what is potentially within that thing. Something can be led thus from potentiality to actuality only by something else which is already actualized. -- Aquinas Abelard and Heloise St Thomas Aquinas Logic + Faith St. Bernard of Clairvaux and Hildegard of Bingen 12th century 13th century