SOURCES, AND CREDIT TO:
- http://webpath.follettsoftware.com/resource/viewurl?encodedUrl=ro64b5gCJeMjSqlUJygrT9G3IO36dj2dwO4u5PoHH3E&version=1&appsignature=Destiny&appversion=10.1.3.1+%28AU1%29
- http://webpath.follettsoftware.com/resource/viewurl?encodedUrl=_wjp4Y8msr4AJ8LfMxE68491npXLTcAq_0EYJ6Kqx9I&version=1&appsignature=Destiny&appversion=10.1.3.1+%28AU1%29
- http://webpath.follettsoftware.com/resource/viewurl?encodedUrl=ytShbPhXhHaaSxITA330TRYC4i6_5DuH9fkhMZCaDQ0&version=1&appsignature=Destiny&appversion=10.1.3.1+%28AU1%29
- http://webpath.follettsoftware.com/resource/viewurl?encodedUrl=Mmq97epTmKTTIG0r5Se30SxXAiCeaVdKnrCpmHVI__I&version=1&appsignature=Destiny&appversion=10.1.3.1+%28AU1%29
- Science Biographies; Descartes, René du Perron; Pages 58 - 60.
- http://www.choosinghats.com/2009/12/pragmatic-point-the-failure-of-the-cartesian-method-of-doubt/
- https://www.google.com/imghp?hl=en&tab=wi