Plato, Aristotle, Bacon and Descartes, as well... successors... [e.g.,] John Stuart Mill, believed that there existed a method of finding scientific truth. ...[L]ater ...slightly more sceptical ...methodologists ...believed that there existed a method, if not of finding a true theory, then ...of ascertaining whether ...some ...hypothesis was true; or (even more sceptical) whether some ... hypothesis was ...'probable' ...