Title: Meditations of Descartes
Description: No philosophy summaries on this site ?! I'm scared to try, but I'll get this one started. The short answer -- if you haven't read this, read it!

Summary: it's really scary to be alive. I mean, couldn't we just be dreaming, plugged into the matrix, or being toyed with by a really smart and tricky evil demon? Descartes wants to ask -- if we assume that a really evil demon is toying with me and trying her best to deceive me, is there anything I can know for certain? Descartes thinks that I can know that I am, at least as long as I think, that I can know a little bit more about (thinking) me, that I can know that another (God) exists, and that I can know that corporeal things exist, not just in my mind, but in the world. Hope this helps!