I Think; Therefore I Am.

I Know That I Exist; The Question Is, What Is This 'i' That 'i' Know.

Perfect Numbers Like Perfect Men Are Very Rare.

This Result Could Have Been Achieved Either By His [god] Endowing My Intellect With A Clear And Distinct Perception Of Everything About Which I Would Ever Deliberate, Or Simply By Impressing The Following Rule So Firmly Upon My Memory That I Could Never Forget It: I Should Never Judge Anything That I Do Not Clearly And Distinctly Understand.

Be That As It May, There Is Fixed In My Mind A Certain Opinion Of Long Standing, Namely That There Exists A God Who Is Able To Do Anything And By Whom I, Such As I Am, Have Been Created. How Do I Know That He Did Not Bring It About That There Is No Earth At All, No Heavens, No Extended Thing, No Shape, No Size, No Place, And Yet Bringing It About That All These Things Appear To Me To Exist Precisely As They Do Now?

I Should Consider That I Know Nothing About Physics If I Were Able To Explain Only How Things Might Be, And Were Unable To Demonstrate That They Could Not Be Otherwise.