I Think; Therefore I Am.

For How Do We Know That The Thoughts Which Occur In Dreaming Are False Rather Than Those Others Which We Experience When Awake, Since The Former Are Often Not Less Vivid And Distinct Than The Latter?

Human Wisdom Remains Always One And The Same Although Applied To The Most Diverse Objects And It Is No More Changed By Their Diversity Than The Sunshine Is Changed By The Variety Of Objects Which It Illuminates.

My Third Maxim Was To Try Always To Conquer Myself Rather Than Fortune, And To Change My Desires Rather Than The Order Of The World, And Generally To Accustom Myself To Believing That There Is Nothing Entirely In Our Power Except Our Thoughts, So That After We Have Done Our Best Regarding Things External To Us, Everything In Which We Do Not Succeed Is For Us Absolutely Impossible.

There Is A Little Gland In The Brain In Which The Soul Exercises Its Functions In A More Particular Way Than In The Other Parts.

When I Consider This Carefully, I Find Not A Single Property Which With Certainty Separates The Waking State From The Dream. How Can You Be Certain That Your Whole Life Is Not A Dream?