In the 17th century , Leibniz , Thomas Hobbes and René Descartes explored the possibility that all rational thought could be made as systematic as algebra or geometry . Hobbes famously wrote in Leviathan : " reason ain't nothing but reckoning " . Leibniz envisioned a universal language of reasoning ( his characteristica universalis ) which would reduce argumentation to calculation , so that " there would be no more need of disputation between two philosophers than between two accountants . For it would suffice to take their pencils in hand , down to their slates , and to say each other ( with a friend as witness , if they liked ) : Let us calculate . " These philosophers had begun to articulate the physical symbol system hypothesis that would become the guiding faith of AI research .