How Do We Know That Anything Really

I Can Doubt Everything, Except One Thing, And That Is The Very Fact That I Doubt. Simply Put - I Think, Therefore I Am

Omnia Apud Me Mathematica Fiunt.

If You Would Be A Real Seeker After Truth, It Is Necessary That At Least Once In Your Life You Doubt, As Far As Possible, All Things.

Whatever I Have Up Till Now Accepted As Most True And Assured I Have Gotten Either From The Senses Or Through The Senses. But From Time To Time I Have Found That The Senses Deceive, And It Is Prudent Never To Trust Completely Those Who Have Deceived Us Even Once.

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.